tTNIVEBSITY  OF  CALIFOBNIA  PUBLICATIONS 

COLLEGE  OF  AGRICULTURE 

AGRICULTURAL  EXPERIMENT  STATION 

BERKELEY,  CALIFORNIA 


I.  FUMIGATION  WITH  LIQUID 
HYDROCYANIC  ACID 


BY 
H.  J.  QUAYLE 


II.  PHYSICAL  AND    CHEMICAL 

PROPERTIES   OF   LIQUID 

HYDROCYANIC  ACID 

BY 
GEO.  P.  GRAY  AND  E.  R.  HULBIRT 


BULLETIN  No.  308 

JUxVE,  1919 


UNIVERSITY   OF  CALIFORNIA   PRESS 

BERKELEY 

1919 


Benjamin  Ide  Wheeler,  President  of  the  University. 

EXPEEIMENT  STATION  STAFF 

HEADS    OF   DIVISIONS 

Thomas  Forsyth  Hunt,  Director. 
Edward  J.  Wickson,  Horticulture  (Emeritus). 

Herbert  J.  Webber,  Director  Citrus  Experiment  Station;  Plant  Breeding. 
Hubert  E.  Van  Norman,  Vice-Director;  Dairy  Management. 
William  A.  Setchell,  Botany. 
Myer  E.  Jaffa,  Nutrition. 
Charles  W.  Woodworth,  Entomology. 
Ealph  E.  Smith,  Plant  Pathology. 
J.  Eliot  Coit,  Citriculture. 
John  W.  Gilmore,  Agronomy. 
Charles  F.  Shaw,  Soil  Technology. 

John  W.  Gregg,  Landscape  Gardening  and  Floriculture. 
Frederic  T.  Bioletti,  Viticulture  and  Enology. 
Warren  T.  Clarke,  Agricultural  Extension. 
John  S.  Burd,  Agricultural  Chemistry. 
Charles  B.  Lipman,  Soil  Chemistry  and  Bacteriology. 
Clarence  M.  Haring,  Veterinary  Science  and  Bacteriology. 
Ernest  B.  Babcock,  Genetics. 
Gordon  H.  True,  Animal  Husbandry. 
James  T.  Barrett,  Plant  Pathology. 
Fritz  W.  Woll,  Animal  Nutrition. 
Walter  Mulford,  Forestry. 
W.  P.  Kelley,  Agricultural  Chemistry. 
H.  J.  Quayle,  Entomology. 
J.  B.  Davidson,  Agricultural  Engineering. 
Elwood  Mead,  Eural  Institutions. 
H.  S.  Eeed,  Plant  Physiology. 
J.  C.  Whitten,  Pomology. 
IFrank  Adams,  Irrigation  Investigations. 
C.  L.  Eoadhouse,  Dairy  Industry. 
Frederick  L.  Griffin,  Agricultural  Education. 
John  E.  Dougherty,  Poultry  Husbandry. 
S.  S.  Eogers,  Olericulture. 
J.  G.  MooDEY,  Assistant  to  the  Director. 
Mrs.  D.  L.  Bunnell,  Librarian. 

DIVISION  OF  ENTOMOLOGY 

Citrus  Experiment  Station  at  Eiverside 

H.  J.  Quayle  *A.  F.  Swain 

Hugh  Knight 

Division  of  Entomology  at  Berkeley 

C.  W.  Woodworth  G.  P.  Gray 

W.  B.  Herms  S.  B.  Freeborn 

E.  C.  Van  Dyke  G.  A.  Coleman 

E.  O.  Essig  H.  H.  Severin 

E.  E.  DeOng 


t  In  co-operation  with   office  of  Public  Eoads  and  Eural  Engineering,  U.   S. 
Department  of  Agriculture. 

*  In  war  service. 


I.  FUMIGATION    WITH   LIQUID 
HYDROCYANIC   ACID^ 

By  H.  J.  QUAYLE2 


INTRODUCTION 

Liquid  hydrocj^aiiic  acid^  was  first  used  largely  in  experimental 
tests  in  1916  and  on  an  extensive  commercial  basis  in  1917  for  the 
fumigation  of  citrus  trees  in  California.^  The  inauguration  of  this 
new  method  of  fumigation  has  brought  up  a  number  of  points  on 
which  information  is  needed.  Among  the  more  important  of  these 
from  the  standpoint  of  the  grower  and  fumigator  are :  the  killing 
efficiency  as  compared  with  the  pot  and  machine  methods  of  generation 
of  the  gas ;  the  diffusion  of  the  gas  under  the  tent ;  effect  of  temper- 
ature and  humidity  on  such  diffusion ;  possible  injury  to  the  fruit  and 
foliage ;  injury  when  the  liquid  itself  comes  in  contact  with  different 
parts  of  the  tree ;  the  action  of  the  liquid  on  the  tents ;  the  best  methods 
of  handling  the  liquid  in  the  field ;  the  precautions  to  be  observed  in 
such  handling;  and  the  cost  of  the  liquid  method  as  compared  with 
other  methods  of  fumigation.  An  attempt  is  made  in  the  following 
pages  to  give  some  information  on  these  points  as  based  on  two  seasons* 
experience  with  liquid  hydrocj^anic  acid.  Other  important  questions 
related  to  the  physical  and  chemical  properties  of  the  material  are 
discussed  in  Part  II  of  this  bulletin. 


1  Paper  no.  58,  University  of  California,  Graduate  School  of  Tropical  Agriculture 
and  Citrus  Experiment  Station,  Eiverside,  California. 

2  Acknowledgment  is  made  of  the  assistance  of  Mr.  A.  F.  Swain  in  1917  and 
Mr.  Hugh  Knight  in  1918  in  carrying  on  the  experiments  on  which  this  bulletin 
is  based. 

3  Hydrocyanic  acid  (HCN)  is  a  liquid,  but  since  it  has  never  been  used  until 
recently  in  this  form  for  fumigation  purposes  it  seems  necessary,  to  avoid  con- 
fusion, to  add  the  superfluous  word  ''liquid".  The  term  for  the  same  material 
which  has  gained  common  practical  acceptance  is  ' '  liquid  gas, ' '  which  appears 
to  be  still  less  desirable.  Another  name  wlich  would  correctly  apply  is  ''prussic 
acid. ' ' 

4  Under  the  title  ' '  Anhydrous  Liquid  Hydrocyanic  Acid  for  Fumigation 
Purposes,"  Mr.  C.  W.  Mally  published  an  article  in  the  South  African  Journal 
of  Science  for  October,  1915,  giving  an  account  of  fi^migation  tests  for  the 
mealy  bug,  Pseudococcus  capensis,  on  the  grape.  This  is  the  first  record  of  the 
use  of  hydrocyanic  acid  as  a  liquid  for  fumigation  purposes  that  has  come  to 
our  notice. 


394  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

Some  of  the  first  tests  with  cyanide  fumigation  for  citrus  trees  in 
1886  involved  the  use  of  a  generator  outside  of  the  tented  tree.^  This 
outside  generator  w^as  soon  discarded  for  earthenware  pots,  which 
were  placed  under  each  tree,  and  the  pot  method  of  generation  was 
in  use  exclusively  until  the  season  of  1914,  when  the  outside  generator 
was  again  adopted.  This  portable  generator,*^  however,  was  very 
different  from  the  crude  generator  of  1886.  It  was  known  as  the 
' '  Owl  Fumigating  Machine, '  ''^  and  this  generator  utilized  for  the  first 
time  a  solution  of  sodium  cyanide.  During  the  last  two  or  three  years 
the  portable  generator  known  as  the  "Cyanofumer",  an  improved 
machine,  has  been  widely  used.  These  older  methods  promise  to  be 
largely,  if  not  entirely,  supplanted  in  the  near  future  by  the  use  of 
liquid  hydrocyanic  acid. 


NATUEE  OF  LIQUID  HYDEOCYANIC  ACID  AND  PEECAUTIONS  TO  BE 

OBSEEVED  IN  HANDLING  IT 

Liquid  hydrocyanic  acid  has  been  known  to  chemists  for  many 
years,  but  probably  because  of  its  instability  and  its  very  poisonous 
nature,  as  well  as  the  heretofore  little  actual  need  thereof,  it  has  not 
been  manufactured  on  a  large  scale.  It  is  a  colorless  liquid,  less  than 
three-fourths  the  weight  of  water,  having  a  specific  gravity  of  0.6969 
at  18°  C.  It  is  also  very  volatile  and  boils  at  a  temperature  of  26.5  C 
or  79.7  F.« 

Because  of  its  very  high  volatility,  hydrocyanic  acid  gas  is  rapidly 
given  off  from  the  surface  of  the  liquid,  and  thus  there  is  danger  in 
breathing  in  an  atmosphere  close  to  an  open  container.  More  gas 
will  be  given  off  as  the  surface  of  the  liquid  is  increased  and  also  in 
higher  temperatures.  The  greatest  surface  is  provided,  and  hence 
there  is  greatest  danger  when  the  liquid  is  sprayed  or  spattered.  If 
there  is  any  appreciable  movement  of  the  atmosphere  the  operator  is 
reasonably  safe  if  he  keeps  to  the  windward  side  of  the  exposed  liquid. 
In  any  operation  giving  the  material  an  opportunity  to  vaporize,  such 
as  filling  or  emptying  the  machine  or  containers,  the  apparatus  should 


^  Morse,  F.  W.,  The  Use  of  Gases  against  Scale  Insects.  Bull.  71,  California 
Agricultural  Experiment  Station,  1886. 

G  Gray,  Geo.  P.,  New  Fumigating  Machines.  Monthly  Bull.  California  State 
Commission  of  Horticulture,  vol.  4,  no.  2,  p.  68. 

7  This  machine  was  invented  by  Mr.  Wm.  Din*;le  of  Los  Angeles,  and  Mr. 
Dingle,  together  with  his  brother,  Irwin  Dingle,  also  deserve  the  credit  fr^  the 
inauguration,  on  a  commercial  basis,  of  the  use  of  liquid  hydrocyanic  acid. 

8  The  Cyanide  Industry  by  Eobine  &  Lenglen,  translated  by  Le  Clerc,  p.  16, 
1906. 


FUMIGATION  WITH  LIQUID  HYDROCYANIC  ACID  395 

be  arranged  so  that  it  is  unnecessary  for  the  operator  to  hold  any- 
thing in  place,  and  thus  to  avoid  danger.  Since  the  vapor  is  inflam- 
mable, flame-lights  should  be  kept  away  from  near  the  exposed  liquid. 

Liquid  hydrocyanic  acid  should  be  kept  as  cool  as  possible,  and 
under  ordinary  circumstances  this  can  be  done  by  surrounding  the 
container  with  cloth  or  sacking  which  is  kept  continuously  moist. 
The  containers  should  be  in  the  shade  and  preferably  where  there  is 
a  free  circulation  of  air.  If  the  liquid  is  spilled  on  the  hands  there 
is  no  danger  (if  there  are  no  cuts  or  abrasions)  from  the  actual  contact 
of  the  liquid,  though  there  may  be  danger  from  the  gas  given  off. 

From  our  experience  in  the  field,  the  most  important  precaution 
(and  it  would  seem  the  most  needless  to  mention)  for^  operators  to 
observe  in  the  handling  of  liquid  hydrocyanic  acid  is  not  to  inhale 
in  an  atmosphere  highly  charged  with  the  gas,  and  therefore  to  turn 
away  when  any  liquid  is  exposed  or  get  into  the  fresh  air  before 
inhaling  again.  For  emergencies  a  gas  mask  may  be  a  desirable  part 
of  the  equipment  of  a  fumigation  crew. 


THE  PLANT  FOR  THE  MANUFACTURE  OF  LIQUID  HYDROCYANIC  ACID 

The  first  unit  of  the  original  plant  for  the  manufacture  of  liquid 
hydrocyanic  acid  in  California  or  elsewhere,  on  a  commercial  scale, 
is  shown  in  figure  1.  The  process  is  comparatively  simple.  All  that 
is  necessary  is  to  subject  the  gas,  which  is  generated  in  the  usual  way, 
to  a  sufficiently  low  temperature,  when  it  will  condense  even  without 
pressure,  or  only  such  pressure  as  is  exerted  by  the  gas  itself  in  the 
process  of  generation.  The  plant  (see  fig.  2)  consists  essentially  of 
generators  for  the  generation  of  the  gas  from  sodium  cyanide,  sulfuric 
acid,  and  water,  and  a  condensing  system  where  the  gas  is  conducted 
into  numerous  flues  which  are  bathed  in  cold  brine  from  the  refriger- 
ation plant.  The  first  product,  which  contains  considerable  water,  is 
then  distilled,  which  process  separates  most  of  the  hydrocyanic  acid 
from  the  water,  yielding  a  product  having  a  purity  of  95  per  cent  or 
higher. 

The  improvement  possible  in  the  present  plant  is  to  reduce  the 
waste  in  the  liquefaction  process  in  order  that  a  greater  amount  may 
be  recovered  from  a  given  amount  of  sodium  cyanide.  During  the 
past  year  approximately  80  per  cent  of  the  total  cyanogen  has  been 
recovered,  which  is  equivalent  to  about  14.8  gallons  or  86  pounds  of 
the  anhydrous  liquid  from  a  case.  The  total  weight  of  anhydrous 
hydrocyanic  acid  in  a  case  of  200  pounds  of  sodium  cyanide  (51-52 


396 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


per  cent  cyanogen)  is  108  pounds.^  It  is  scarcely  possible,  commer- 
cially, to  recover  the  total  amount  of  108  pounds  from  200  pounds  of 
sodium  cyanide,  although  this  amount  will  be  more  nearly  approached 
as  more  improvements  are  made  in  the  plant. 


r  '  '- 
■>  • 

4   *  ^fl 

.^li 

*«--*;.v"'^? 

'  -^  ,   I'M 

III 

Fig.  1 — First  unit  of  original  plant  for  the  manufacture  of  liquid  hydrocyanic 
acid.     Azusa,  California.     May,  1917. 


THE  ATOMIZING  MACHINE 

After  the  liquid  is  transported  from  the  central  plant  to  the  field 
in  proper  containers  it  is  placed  in  a  machine,  such  as  is  indicated  in 
figures  3  and  4.  The  atomizing  machine  consists  of  a  tank  holding 
two  and  one-half  gallons  of  the  liquid,  a  graduate  for  the  measurement 
of  the  dosage,  and  a  pump  and  spray  nozzles  for  the  atomizing  of  the 
liquid.  By  the  upward  stroke  of  the  plunger,  near  the  graduated 
scale  (see  fig.  4),  the  liquid  is  allowed  to  run  into  the  graduate  and 
by  the  downward  stroke  it  is  forced  into  the  coil  as  shown.  Then 
by  the  operation  of  the  air  pump  on  the  right  the  liquid  is  forced  out 
through  nozzles  at  the  end  of  the  exit  tube  into  a  fine  misty  spray, 
which  is  immediately  transformed  into  a  gas. 

»  See  Table  I  in  Part  II  of  this  bulletin. 


FUMIGATION  WITH  LIQUID  HYDROCYANIC  ACID 


397 


398 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


GEADUATION  AND  OPEEATION  OF  THE  ATOMIZING  MACHINE 

The  atomizing  machine  in  use  during  the  season  of  1918  was 
graduated  on  the  basis  of  the  recovery  of  14  gallons  of  liquid  hydro- 
cyanic acid  from  200  pounds  of  cyanide;  that  is,  the  liquid  recovered 
was  made  to  go  as  far,  according  to  our  present  schedules  of  dosage, 
as  the  original  case  of  cyanide  by  other  methods  of  generation.  There 
are  3200  ounces  in  a  case  of  sodium  cyanide  and  1792  fluid  ounces 


Fig.  3 — Atomizing  machine,  in  use  season  of  1917,  for  atomizing  liquid  hydro- 
cyanic acid  under  tent. 


in  14  gallons.  This  amount  of  fluid  was  therefore  divided  into  3200 
parts,  so  that  .560  fluid  ounce  was  used  as  the  equivalent  of  1  ounce 
of  the  solid  sodium  cyanide.  The  actual  amount  of  hydrocyanic  acid 
in  .56  fluid  ounce  of  95  per  cent  hydrocyanic  acid  may  be  calculated 
from  the  data  in  Table  I,  Part  II,  as  follows : 

Fourteen  gallons  of  liquid  of  this  purity  weighs  5.956  X  14  X  16, 
or  1334  ounces,  but  only  95  per  cent  of  this  weight  is  hydrocyanic 
acid,  the  remainder  being  impurities,  mostly  water.  The  amount  of 
absolute  hydrocyanic  acid  is  1334  X  -95,  or  1265.4  ounces.  Dividing 
this  by  3200,  we  obtain  .395  as  the  weight  in  ounces  of  actual  hydro- 
cyanic acid  in  the  .560  fluid  ounce  of  liquid  delivered  by  the  atomizer 
as  the  equivalent  of  1  ounce  of  sodium  cyanide. 


FUMIGATION  WITH  LIQUID   HYDROCYANIC  ACID 


399 


By  other  methods  of  generation,  the  pot  and  portable  generator, 
we  assume  that  about  90  per  cent,  at  least,  of  the  total  gas  is  evolved.^^ 
Under  this  assumption,  1  ounce  of  sodium  cyanide  would  yield  a 
weight  of  .486  ounce  of  absolute  hydrocyanic  acid.  If  this  amount 
were  converted  into  a  liquid  containing  5  per  cent  of  water  the  volume 
would  be  .693  fluid  ounce. 

The  dosage  applied  by  the  liquid  system  has  been  only  80  per  cent 
of  that  applied  by  the  older  methods.     If  the  same  dosage  is  to  be 


'IHtf^*^1iwwi 


Fig.  4 — Atomizing  machine  in  use  season  of  1918. 


applied,  .693  fluid  ounce  of  95  per  cent  liquid  (or  .675  fluid  ounce  of 
98  per  cent  liquid)  must  be  used  as  the  equivalent  of  the  yield  from 
1  ounce  of  sodium  cyanide  when  the  gas  is  generated  by  the  older 
methods. 

The  above  figures  have  all  been  given  in  the  American  system  of 
weights  and  measures.  More  finely  graduated  cylinders  can  be  ob- 
tained, marked  in  cubic  centimeters  and  fractions,  and  are  commonly 
used  to  test  the  accuracy  of  delivery  from  the  atomizing  machine. 


10  H.  D.  Young,  as  reported  in  Circular  139  of  the  California  Agricultural 
Experiment  Station,  determined  that  the  Cyanofumer  yielded,  under  the  best 
working  conditions,  about  95  per  cent  of  the  total  gas.  It  has  usually  been 
assumed  that  the  yield  from  the  pot  method  varied  from  85  to  95  per  cent.  As 
a  conservative  average  of  both  methods  we  have  given,  as  above,  a  90  per  cent 
yield. 


400  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

The  following  metric  equivalents  will  be  useful  in  checking  up  their 
delivery. 

.693  fluid  oz.  =  20.5  c.c.  (full  dose  of  95%  HCN). 
.675  fluid  oz.  =  19.9  c.c.  (full  dose  of  98%  HCN). 
.560  fluid  oz.  =  16.5  c.c.   (80%  dose  as  applied  last  season). 

To  insure  proper  dosage,  it  is  important  that  the  atomizing 
machine  be  kept  in  good  working  order.  The  machine  should  be 
emptied  of  the  hydrocyanic  acid  after  each  night's  run  to  avoid 
unnecessary  action  of  the  material  on  the  parts  of  the  machine,  and 
the  machine  allowed  to  remain  filled  with  water  until  it  is  used  again. 
The  machine  should  be  tested  frequently  to  see  that  the  dose,  as 
graduated,  is  delivered  at  the  end  of  the  exit  tube.  This  is  readily 
done  by  removing  the  nozzles  and  attaching  a  short  piece  of  rubber 
tubing  to  conduct  the  liquid  into  a  suitably  marked  graduate.  If, 
for  instance,  an  ounce  on  the  graduate  of  the  machine  represents 
16.5  cubic  centimeters,  when  the  machine  is  set  for  a  10-ounce  charge 
there  should  be  165  cubic  centimeters  delivered  into  the  graduate. 
A  convenient  graduate  is  furnished  by  running  a  10-ounce  charge 
into  a  long,  narrow  bottle  and  marking  the  height  of  the  liquid  by 
means  of  a  file.  Water  may  be  used  in  measuring  the  accuracy  of 
the  pump,  but  there  may  be  more  water  actually  delivered  than  liquid 
hydrocyanic  acid,  so  that  it  is  more  accurate  to  use  the  liquid  itself, 
in  which  case  the  proper  precautions  regarding  safety  must  be  kept 
in  mind. 


EFFECT  OF  LIQCTID  HYDEOCYANIC  ACID  ON  THE  FRUIT  AND  FOLIAGE 

Gas  from  liquid  hydrocyanic  acid  will  injure  the  fruit  and  foliage 
if  used  in  excess  in  much  the  same  way  as  the  gas  generated  by  other 
methods.  In  many  cases,  however,  particularly  if  the  fumigation  is 
done  during  low  temperatures,  the  injury  is  often  greater  in  the 
lower  than  in  the  upper  half  of  the  tree.  This  is  accounted  for  under 
''Diffusion  of  the  Gas." 

When  the  liquid  itself  comes  in  contact  with  fruit  or  foliage  severe 
burning  occurs,  as  may  be  seen  where  the  material  is  atomized  in 
delivering  the  charge  under  the  tent.  This  is  not  very  serious,  but 
in  the  case  of  much  low-hanging  fruit  it  is  of  some  consequence.  Such 
injury  may  be  partly  avoided  by  having  a  longer  exit  tube  and  ad- 
justing the  nozzles  to  direct  the  spray  at  a  smaller  angle,  so  as  to 
avoid  the  fringe  of  low-hanging  fruit  and  foliage  around  the  outside 
of  the  tree.     There  is  no  danger  if  the  liquid  strikes  the  trunk,  at 


FUMIGATION  WITH  LIQUID  HYDROCYANIC  ACID  401 

least  of  old  trees.  We  have  applied  the  spray  directly  to  the  trunk 
of  two-year-old  trees  also  without  doing  any  injury.  Possibly  under 
conditions  very  unfavorable  to  evaporation,  as  during  cold  and  wet 
weather,  some  injury  might  occur  to  the  trunk  of  young  trees. 

EFFECT  OF  LIQUID  HYDEOCYANIC  ACID  ON  TENTS 

One  of  the  objections  of  the  older  methods  of  fumigation  was  the 
injury  that  was  often  done  to  tents.  Liquid  hydrocyanic  acid  has  no 
effect  on  fabrics  and  there  is  no  residue  or  acid  anywhere  around  that 
may  do  such  injury. 

COST   OF   USING  LIQUID    HYDEOCYANIC    ACID    AS   COMPAEED   WITH 
THE  OTHEE  METHODS  OF  FUMIGATION 

During  the  past  tAvo  years  there  has  been  little  difference  in  the 
cost  of  using  the  liquid  as  compared  with  the  other  methods  of  fumi- 
gation. Distance  from  the  manufacturing  plant  and  other  factors 
make  the  cost  variable.  However,  when  the  manufacture  of  the  liquid 
is  better  stabilized  the  cost  of  fumigation  should  be  appreciably  re- 
duced. Even  if  the  actual  material  will  not  cost  less,  there  will  be  a 
saving  on  the  tents  as  well  as  less  expense  in  handling  the  liquid  in 
the  field. 

When  sodium  cyanide  (51-52  per  cent  cyanogen)  is  worth  thirty 
cents  per  pound,  the  absolute  liquid  hydrocyanic  acid  would  be  worth 
fifty-five  and  five-ninths  cents  per  pound.  But  it  is  not  possible, 
commercially,  to  recover  100  per  cent,  and,  moreover,  the  product 
recovered  would  not  have  a  purity  of  100  per  cent.  Neither  is  the 
cost  of  liquefaction  included  in  the  above  price. 

If  but  90  per  cent  is  recovered  in  the  liquid  form,  the  corresponding 
price  (solid  cyanide  at  thirty  cents)  of  the  liquid  would  be  sixty- two 
cents  per  pound.  When  a  90  per  cent  recovery  contains  5  per  cent 
water,  the  corresponding  price  per  pound  of  the  liquid  would  be  be- 
tween fifty-eight  and  fifty-nine  cents  per  pound. 

DIFFUSION  OF  THE  GAS 

From  previous  experiments^^  it  has  been  shown  that  with  the  gas 
generated  by  the  pot  or  portable  generator  there  is  a  greater  concen- 
tration of  the  gas  in  the  upper  half  of  the  tree,  and  consequently 

11  Quayle,  H.  J.,  Cyanide  Fumigation — Diffusion  of  Gas  Under  Tent  and 
Shape  of  Tree  in  Eelation  to  Dosage.  Jour.  Economic  Entomology,  vol.  11, 
no.  3,  p.  294,  1918. 


402  UNIVERSITY   OF    CALIFORNIA — EXPERIMENT   STATION 

better  results  on  the  scale  insects  in  that  part  of  the  tree.  "With  the 
gas  which  arises  from  the  liquid  under  present  manipulations  the 
conditions  are  exactly  reversed  and  the  better  results  occur  in  the 
lower  half  of  the  tree.  Of  the  three  locations — top,  center,  and  bottom 
of  the  tree — the  gas  from  the  liquid  is  most  effective  at  the  bottom, 
next  at  the  center,  and  least  at  the  top.  With  the  pot  generation 
there  is  not  much  difference  in  effectiveness  between  the  top  and 
center  of  an  average  sized  tree,  but  there  is  a  decided  decrease  in 
effectiveness  at  the  bottom. 

In  field  work  the  lower  half  of  the  tree  is  examined.  The  upper 
half,  and  particularly  the  top  of  the  tree,  is  not  examined  unless  some 
special  effort  is  made.  This  fact  is  actually  favorable  to  the  results 
with  the  liquid  and  unfavorable  to  the  results  with  the  pots  or  port- 
able generator.  But  there  are  more  scales,  in  most  cases,  in  the  lower 
than  in  the  upper  half  of  the  tree. 

In  1917  an  amount  of  liquid  hydrocyanic  acid  equal  to  only  60 
per  cent  of  the  total  gas  in  a  given  amount  of  cyanide  was  compared 
with  90  per  cent  of  the  total  gas  from  the  same  amount  generated  by 
the  pot  or  portable  generator.  There  was  no  difference  in  results  by 
the  ordinary  field  examination,  but  there  was  a  marked  difference  in 
results  by  our  own  tests.  In  judging  the  results  of  the  liquid  as  com- 
pared with  other  methods  of  fumigation  in  the  field,  therefore,  allow- 
ance must  be  made  for  the  necessary  inaccuracy  of  tests  under  field 
conditions,  and  also  for  the  fact  that  the  examination  is  made  in  the 
lower  half  of  the  tree,  where  the  liquid  is  more  effective. 

The  manner  of  diffusion  of  hydrocyanic  acid  gas  is  different 
according  to  whether  it  comes  from  liquid  hydrocyanic  acid  or  from 
a  generator  where  the  cyanide,  sulfuric  acid,  and  water  are  combined. 
In  the  former  case,  vaporization  takes  place  near  the  ground  and 
the  gas  gradually  diffuses  upward ;  while  in  the  latter  the  gas  goes 
quickly  to  the  top  of  the  tree  and  gradually  diffuses  downward.  This 
has  been  shown  by  the  effects  of  the  gas  in  first  overcoming  active 
insects  at  the  bottom  of  the  tree  in  one  case  and  at  the  top  of  the  tree 
in  the  other.  And  if  the  exposure  is  prolonged  for  an  hour  the  final 
effect  on  the  insects  shows  the  same  difference ;  that  is,  in  the  latter 
case  more  recover  at  the  bottom  and  in  the  former  case  more  recover 
at  the  top. 

The  manner  of  diffusion  of  the  gas  from  the  liquid,  as  explained 
above,  is  better  adapted,  we  believe,  to  the  killing  of  scales  on  the  tree 
than  the  manner  of  diffusion  from  the  pot  or  portable  generator, 
particularly  since  most  of  the  scales  occur  in  the  lower  part  of  the 
tree,  and  for  this  reason  it  is  possible  that  the  liquid  equivalent  may 


FUMIGATION  WITH  LIQUID  HYDROCYANIC  ACID  403 

be  slightly  reduced.  The  question  may  properly  be  raised  whether 
more  scales  occur  in  the  lower  half  of  the  tree  because  the  older 
methods  of  fumigation  failed  to  kill  them  as  well  there,  but  we  believe 
that  the  habits  of  the  insects  also  favor  that  location. 


EFFECT  OF  TEMPERATURE  ON  DIFFUSION  OF  HYDROCYANIC 

ACID  GAS 

The  question  of  temperature  may  be  more  vitally  concerned  with 
the  diffusion  of  gas  from  the  liquid  than  from  the  pot  or  portable 
generator,  although  it  is  a  factor  in  any  method  of  fumigation.  The 
higher  temperatures  hasten  the  vaporization  and  diffusion  of  gas  from 
the  liquid  and  insure  a  better  killing  at  the  top  of  the  tree.  On  the 
other  hand,  the  higher  temperatures  aid  in  the  diffusion  of  the  gas 
downward  with  the  pot  method  where  it  is  first  concentrated  in  the 
top  of  the  tree.  Our  experiments  have  pointed  strikingly  to  the 
tendency  that  the  higher  the  temperature  the  more  uniform  is  the 
distribution  in  all  parts  of  the  tree.  As  the  temperature  decreases 
the  divergence  in  results  increases  between  the  top  and  bottom  of  the 
tree,  in  case  of  the  liquid  in  favor  of  the  bottom  and  in  case  of  the  pot 
in  favor  of  the  top  of  the  tree. 

In  the  pot  or  portable  generator  the  actual  gas  is  produced  more 
or  less  regardless  of  the  atmospheric  temperature,  since  the  different 
chemicals  when  brought  in  contact  will  act  upon  one  another  to  gen- 
erate the  gas,  during  which  action  heat  is  also  produced,  and  the 
warm  gas  readily  rises.  With  the  liquid  vaporization  must  first  occur, 
and  low  temperature,  as  well  as  high  humidity,  tends  to  retard  such 
action.  Moreover,  when  the  gas  is  actually  formed  it  is  a  cold  gas 
and  has  a  smaller  tendency  to  rise  in  the  tent.  The  atomizing  of  the 
liquid  is  in  itself  a  cooling  process.  The  bulb  of  a  thermometer  when 
held  for  a  few  moments  before  the  nozzles  as  liquid  hydrocyanic  acid 
was  being  atomized  showed  a  drop  in  temperature  from  70°  F  to 
—4°  F. 

The  following  table  gives  the  total  average  '^kill"  of  ladybird 
beetles  in  the  form  "frees"^^  for  the  1918  series  of  tests,  which  ex- 
tended over  four  months  and  included  the  use  of  about  25,000  insects. 

Bottom  and  center  Top  and  center 

of  tent  of  tent 

Pot   85.7%  killed  91.1%  killed 

Liquid 83.8%  killed  76.9%  killed 


12  The  form  'Hrees"  consisted  of  a  framework  of  wood  in  the  shape  of  an 
ordinary  citrus  tree  over  which  were  placed  ordinary  fumigation  tents.  The 
dimensions  were  26  X  ^1>  thus  representing  fair  sized  trees. 


404  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

From  the  above  it  will  be  noted  that  the  discrepancy  in  efficiency 
with  the  liquid  occurs  in  the  upper  half  of  the  tree.  But  the  experi- 
ments also  showed  that  this  discrepancy  was  greatly  reduced  with  the 
higher  temperatures.  Another  tendency  that  has  been  indicated  is: 
that  a  long  exposure  increases  the  effect  of  the  gas  from  the  liquid. 
This  may  be  due  to  the  slower  diffusion,  as  well  as  the  cooler  gas  from 
the  liquid  actually  escaping  more  slowly  through  the  tent.  By  the 
other  methods  of  fumigation  it  is  quite  well  established  that  there  is 
no  value  in  increasing  the  time  of  exposure  beyond  about  forty-five 
minutes. 

As  to  whether  the  tendency  of  the  gas  from  the  liquid  to  remain 
largely  in  the  lower  half  of  the  tree  during  low  temperatures  is  a 
serious  objection  to  its  practical  use,  or  whether  it  is  practicable  to 
increase  the  exposure,  remains  for  further  experience  to  determine. 
Heating  the  gas,  or  a  better  system  of  atomizing,  or  gasifying  the 
liquid,  are  two  possible  ways  of  overcoming  the  poor  diffusion,  although 
this  might  complicate  the  field  manipulations. 

THE  EFFICIENCY  OF  LIQUID  HYDROCYANIC  ACID  AS  COMPARED 
WITH  POT  AND  MACHINE  GENERATION 

The  killing  efficiency  of  the  liquid  as  compared  with  other  methods 
of  fumigation  was  determined:  {a)  by  comparative  tests  in  a  fuma- 
torium;  (&)  by  comparative  tests  under  form  trees;  (c)  by  compar- 
ative tests  in  the  field;  and  {d)  by  examination  of  commercial  work 
in  the  field. 

In  addition  to  the  scale  insects  of  citrus  trees,  for  which  pests 
fumigation  work  is  carried  on,  ladybird  beetles  were  used  as  an  index 
of  the  results.  Our  two  seasons'  work  with  the  beetles  lead  us  to 
conclude  that  they  are  more  desirable  than  scale  insects  as  furnishing 
a  sharp  index  of  comparative  fumigation  results.  In  the  case  of  scale 
insects,  there  may  be  100  per  cent  killed  with  ordinary  dosages,  where 
these  dosages  vary  as  much  as  25  per  cent.  With  the  highest  dosage 
that  may  be  used  with  safety  to  the  citrus  trees,  some  of  the  beetles 
will  survive,  and  increasing  numbers  will  survive  as  the  dose  is  de- 
creased. It  is  possible  also  to  determine  the  difference  in  results  be- 
tween the  top  and  bottom  of  a  tree,  with  the  beetles  properly  placed, 
while  with  the  scale  insects  occurring  naturally  on  the  tree  it  is  more 
difficult  to  make  such  a  distinction.  All  of  our  results,  however,  are 
based  on  work  both  with  the  beetles  and  the  scale  insects. 

During  the  season  of  1917,  in  our  tests  both  in  the  field  and  under 
form  trees,  the  results  with  the  liquid  were  less  satisfactory  than  the 
results  carried  on  at  the  same  time  with  the  pot  and  cyanofumer. 


FUMIGATION  WITH  LIQUID  HYDROCYANIC  ACID  405 

This  may  be  accounted  for  from  the  fact  that  during  that  season  the 
liquid  was  not  of  high  purity  until  late  in  the  season,  and  also  because 
the  machine  in  use  that  year  was  graduated  on  the  recovery  of  only 
12%  gallons  of  liquid  from  a  case  of  cyanide.  In  our  examination 
of  commercial  fumigation,  however,  there  was  little  if  any  difference 
that  could  be  determined  by  the  results  on  the  scales  in  the  field. 

During  the  season  of  1918  our  own  tests  again  showed  that  the 
liquid  was  slightly  less  efficient  than  the  pot  method,  although  there 
was  a  marked  improvement  over  the  preceding  year.  In  the  field, 
as  in  1917,  no  appreciable  difference  could  be  distinguished.  Tests 
carried  on  with  the  cyanofumer  and  liquid  on  alternate  trees  in  the 
same  tent-throw,  thus  insuring  similar  conditions,  failed  to  distinguish 
any  difference  either  on  beetles  which  were  placed  in  the  tree  or  on 
the  scales  on  the  fruit  and  foliage.  The  results  thus  determined, 
however,  represent  the  effect  on  the  insects  within  six  or  eight  feet  of 
the  ground,  which  fact  is  important  as  discussed  under  the  head  of 
"Diffusion  of  the  Gas." 

In  our  experiments  with  form  "trees"  the  difference  between  the 
pot  and  liquid  methods  was  brought  out  by  considering  the  effect  of 
the  gas  at  three  different  points,  namely,  one  foot  from  the  top,  one 
foot  from  the  bottom,  and  in  the  center  of  the  tree.  When  the  results 
in  the  lower  half  only  were  considered,  there  was  no  important  dif- 
ference between  the  pot  and  liquid  methods.  But  when  the  results 
on  the  upper  part  of  the  tree  were  included,  they  were  more  favorable 
to  the  pot  method. 

While,  so  far  as  field  conditions  and  examination  go  within  seven 
or  eight  feet  of  the  ground,  between  the  liquid  and  the  older  methods 
of  fumigation  the  results  have  shown  little  important  difference,  we 
believe  that  a  greater  recovery  of  liquid  from  a  given  amount  of 
cyanide  is  necessary,  and  that  it  is  desirable  to  increase  the  amount 
given  to  the  tree  over  that  of  the  past  two  years.  Judging  from  the 
field  work,  we  had  come  to  believe  that  when  temperature  conditions 
are  favorable  the  gas  from  the  liquid  must  be  10  to  15  per  cent  more 
effective  than  the  same  amount  of  gas  from  the  pot  or  portable  gen- 
erator. Fourteen  gallons  of  liquid  hydrocyanic  acid  of  96  or  98  per 
cent  purity  recovered  from  200  pounds  of  sodium  cyanide  represent 
only  75  per  cent  of  the  total  available  gas,  while  by  the  other  methods 
90  per  cent  of  the  total  gas  in  200  pounds  was  recovered,  making  a 
difference  of  15  per  cent.  Yet,  during  the  past  year,  the  14  gallons 
of  liquid  was  made  to  cover  the  same  ground  as  200  pounds  of 
sodium  cyanide  generated  by  the  other  methods.  When  the  results 
in  all  parts  of  the  tree  are  considered,  however,  as  shown  by  our 


406  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

comparative  tests  for  two  seasons,  we  believe  that,  under  normal  con- 
ditions, practically  the  equivalent  in  the  actual  amount  of  gas  must  be 
used  to  effect  the  same  results  regardless  of  whether  the  source  of  the 
gas  is  from  liquid  hydrocyanic  acid  or  from  the  pot  or  portable 
generator.  Consequently  90  per  cent  at  least,  representing  17  gallons 
or  100  pounds  of  liquid  hydrocyanic  of  96  or  97  per  cent  purity, 
should  be  recovered  from  200  pounds  of  sodium  cyanide,  and  this 
amount  should  be  made  to  cover  the  same  ground  as  200  pounds  of 
sodium  cyanide  on  the  basis  of  the  dosage  schedules  now  in  use.  This 
would  be  equivalent  to  using  approximately  20  cubic  centimeters  to 
correspond  to  one  ounce  of  sodium  cyanide  (51-52  per  cent  cyanogen). 
(See  discussion  under  ^'Graduation  and  Operation  of  Atomizing 
Machines,"  p.  398  and  table  1,  p.  412.) 


SUMMARY  AND  CONCLUSIONS 

Liquid  hydrocyanic  acid,  a  new  means  of  citrus  fumigation,  first 
used  on  a  commercial  basis  in  1917,  has  rapidly  come  into  favor. 

The  place  where  the  greatest  concentration  of  gas  occurs  under 
the  tent  from  the  liquid  is  practically  the  reverse  of  that  from  the  pot 
or  portable  generator. 

"With  the  former  method  the  most  effective  killing  is  at  the  bottom 
of  the  tree,  while  with  the  latter  the  most  effective  killing  is  at  the  top. 

Aside  from  the  scale  insects,  more  than  75,000  ladybird  beetles 
have  been  used  in  our  comparative  tests  as  an  index  of  results. 

The  use  of  these  insects  has  given  discriminating  data  concerning 
the  diffusion  of  gas  under  the  tent,  as  well  as  on  the  efficiency  of  the 
different  methods  of  fumigation,  and  these  data  have  been  verified  by 
extensive  field  tests. 

The  greatest  possible  yield  is  108  pounds  or  18.56  gallons  of  an- 
hydrous liquid  hydrocyanic  acid  from  200  pounds  of  sodium  cyanide 
(51-52  per  cent  cyanogen). 

The  amount  of  liquid  hydrocyanic  acid  (95-98  per  cent)  that  has 
been  recovered  at  the  plant  during  the  past  year  has  been  about  78 
per  cent  of  the  total  available. 

The  amount  of  gas  evolved  by  the  pot  or  portable  generator  is 
estimated  at  90  per  cent  of  the  total  available  gas. 

During  the  past  year  75  per  cent  of  the  gas  from  a  given  amount 
of  cyanide  in  the  liquid  form  was  made  to  cover  the  same  ground  as  90 
per  cent  from  the  same  amount  by  the  ordinary  methods  of  generation. 


FUMIGATION  WITH  LIQUID  HYDROCYANIC  ACID  407 

Thus,  while  there  has  been  a  discrepancy  of  10  or  15  per  cent  in 
the  actual  amount  of  gas  used  through  the  liquid  method,  the  results 
in  the  field  have  not  indicated  any  important  difference  on  the  scale 
insects. 

Our  own  tests,  however,  both  in  the  field  and  laboratory,  have 
indicated  about  such  difference  as  would  be  expected. 

This  apparent  discrepancy  between  our  own  tests  and  commercial 
work  in  the  field  may  be  accounted  for  through  the  great  variability 
in  field  work  and  by  the  difference,  as  has  been  determined,  in  the 
diffusion  of  the  gas  from  the  different  methods. 

Field  examinations  are  usually  limited  to  an  examination  of  the 
scales  within  six  or  eight  feet  of  the  ground. 

Our  own  tests  have  included  the  top  of  the  tree  as  well.  From 
these  tests,  when  the  results  at  the  center  and  the  bottom  only  were 
considered,  there  was  practically  no  difference  between  the  liquid  and 
the  pot,  which  harmonizes  with  the  results  in  the  field. 

When  the  results  at  the  center  and  top  only  were  considered,  the 
pot  method  was  more  efficient  than  the  liquid  method. 

When  the  results  in  all  parts  of  the  tree  are  considered,  it  is 
necessary  to  use  about  20  cubic  centimeters  of  liquid  hydrocyanic 
acid  (96  or  98  per  cent)  to  equal  one  ounce  of  sodium  cyanide  as 
given  in  the  schedules  of  dosage  now  in  practical  use. 

Units  representing  20  cubic  centimeters  may  therefore  be  sub- 
stituted for  the  ounces,  and  the  atomizing  machines  should  be  gradu- 
ated to  deliver  20  cubic  centimeters  for  each  ounce  called  for  in  the 
schedules. 


II.  PHYSICAL  AND    CHEMICAL   PROPERTIES 
OF  LIQUID  HYDROCYANIC  ACID 

By  GEO.  P.  GRAY  and  E.  R.  HULBIRTi 


The  ready  acceptance  of  liquid  hydrocyanic  acid  hy  fumigators 
during  the  first  year  of  its  commercial  production  strongly  empha- 
sized the  need  of  a  better  knowledge  of  the  physical  and  chemical 
properties  of  a  liquid  of  such  unusual  characteristics.  The  Fruit 
Growers'  Supply  Company,  the  purchasing  organization  of  the 
•California  Fruit  Growers'  Exchange,  were  much  concerned  over  the 
scarcity  of  information  regarding  the  liquid  being  marketed,  and 
financed  an  investigation  of  the  plant  and  product  of  the  Owl  Fumi- 
gating Company  at  Azusa,  California,  during  the  month  of  August, 
1918.  This  preliminary  investigation  not  only  proved  to  be  of  much 
value  to  the  growers  but  also  disclosed  such  a  variety  of  questions 
to  be  answered  that  a  co-operative  arrangement  for  the  continuation 
of  the  investigation  was  made  between  the  supply  company  and  this 
laboratory.  The  following  pages  constitute  a  report  of  these  investi- 
gations.- 

COMMERCIAL  CONSIDERATIONS 

The  questions  of  most  immediate  concern  appeared  to  be  of  a 
commercial  nature.  The  liquid  being  delivered  to  consumers  was  not 
sold  outright,  but  was  delivered  upon  an  exchange  basis.  The  fumi- 
gators purchased  their  own  sodium  cyanide  and  brought  it  to  the  plant 

1  Co-operating  chemist,  representing  the  Fruit  Growers '  Supply  Company. 

2  The  writers  wish  to  express  their  appreciation  of  the  attitude  of  Messrs. 
Ervin  and  WilHam  Dingle,  who  have  extended  to  them  every  courtesy  during 
the  course  of  the  investigation  and  have  given  them  the  freedom  of  their  plant, 
and  have  done  everything  in  their  power  to  facilitate  the  work.  The  Board  of 
Trustees  and  Professor  F.  S.  Hayden,  Principal  of  the  Citrus  Union  High  School, 
have  generously  allowed  the  free  use  of  their  laboratories  and  apparatus.  This 
accommodation  has  greatly  facilitated  the  investigation  by  allowing  the  testing 
laboratory  and  the  liquifying  plant  to  be  located  in  close  proximity.  The 
interest  shown  by  Mr.  R.  S.  Woglum  and  Mr.  H.  D.  Young  of  the  United  States 
Bureau  of  Entomology  in  developing  methods  of  analysis  and  in  the  test  runs 
of  the  plant  has  been  of  great  assistance.  Mr.  F.  W.  Braun,  Mr.  M.  B.  Pattison, 
and  Mr.  J.  D.  Neuls  of  the  Braun  Corporation  have  offered  many  suggestions, 
jjarticularly  concerning  methods  of  analysis.  The  many  accommodations  and 
courtesies  extended  by  Mr.  C.  C.  Hillis,  Mr.  C.  A.  Savage,  and  other  officials  of 
the  Azusa-Covina-Gleudora  Fruit  Exchange  are  much  appreciated. 


PHYSICAL  AND  CHEMICAL  PROPERTIES  OF  HYDROCYANIC  ACID         409 

for  treatment.  The  plant  furnished  the  sulfuric  acid,  generated,  and 
liquefied  the  hydrocyanic  acid  at  a  fixed  charge  per  case  of  sodium 
C3^anide.  There  appeared  to  be  no  well  established  idea  as  to  what 
quantity  of  liquid  should  be  recovered  from  a  case  of  sodium  cyanide 
under  the  operating  conditions  of  the  plant,  though  it  was  generally 
conceded  that  the  quality  of  the  liquid  being  delivered  to  the  consumer 
was  of  good  grade. 

Test  Buns. — In  order  to  determine  the  amount  and  quality  of 
liquid  recovered  from  a  case  of  sodium  cyanide  under  the  operating 
conditions  of  the  plant,  the  owners  offered  to  make  a  test  run  to  be 
carried  on  under  the  supervision  of  a  representative  of  the  Fruit 
Growers'  Supply  Company.  The  results  of  these  tests  were  to  be 
used  as  a  basis  of  settlement  between  fumigator  and  plant.  In  order 
that  the  results  should  be  above  criticism  of  partiality,  the  following 
gentlemen  kindly  accepted  an  invitation  to  be  present  to  witness  the  test 
run :  Messrs.  R.  S.  Woglum,  entomologist,  and  H.  D.  Young,  chemist, 
representing  the  U.  S.  Bureau  of  Entomology ;  Professor  H.  J.  Quayle, 
entomologist,  representing  the  Citrus  Experiment  Station  of  the  Uni- 
versity of  California ;  Mr.  W.  C.  Bass,  chemist,  representing  the  Owl 
Fumigating  Company ;  and  the  senior  writer,  representing  the  Fruit 
Growers'  Supply  Company,  and  unofficially  the  Insecticide  and  Fungi- 
cide Laboratory  of  the  University  of  California.  The  proposed  pro- 
cedure of  the  test  was  outlined  and  agreed  upon  by  the  representatives 
present  as  being  a  fair  one.  Seventeen  cases  of  sodium  cyanide 
(3400  pounds)  were  weighed  out  and  sampled  for  the  test  run.  The 
plant  was  operated  in  the  usual  manner  and  the  yield  of  liquid  was 
weighed  and  sampled.  The  samples  noted  above  were  independently 
analyzed  by  Messrs.  Young,  Bass,  and  Gray.  On  comparing  the 
results  of  analysis  it  was  found  that  the  three  sets  of  results  were 
in  essential  agreement.  Not  being  willing  to  base  conclusions  upon 
a  single  run  of  the  plant,  another  test  was  made  a  week  later  in  a 
similar  manner.  The  liquid  hydrocyanic  acid  recovered  in  the  first 
test  run  was  80.1  per  cent  of  the  greatest  possible  yield;  in  the  second, 
76.3  per  cent ;  an  average  of  78.2  per  cent.  The  average  purity  of  the 
liquid  obtained  in  the  first  run  was  97.57  per  cent ;  in  the  second, 
94.27  per  cent. 

While  the  yield  of  78  per  cent  was  quite  disappointing,  it  must 
be  recognized  that  this  is  an  infant  industry,  and  that  with  increasing 
knowledge  and  experience  with  the  liquid  continual  improvement  in 
all  phases  of  its  manufacture  and  use  may  be  expected.  The  con- 
structors of  the  plant  had  no  previous  work  to  guide  them  in  selection 
of  their  equipment.    There  were  certain  evident  losses  in  the  operation 


410  UNIVERSITY   OF    CALIFORNIA — EXPERIMENT   STATION 

of  the  plant  which  will  doubtless  be  remedied  before  next  season. 
It  also  appears  that  there  are  certain  other  losses,  the  causes  of  which 
are  somewhat  obscure. 

Quality  of  Liquid. — Frequent  analyses  and  tests  have  been  made 
of  the  liquid  being  delivered  to  consumers,  covering  a  period  from 
the  first  of  August  to  the  close  of  the  fumigating  season.  The  average 
purity  of  the  liquid  delivered  to  consumers  has  been  above  95  per  cent 
absolute  hydrocyanic  acid.  Occasional  drums  of  liquid  have  been 
noted  which  were  considerably  below  this  figure.  After  the  plant 
was  supplied  with  hydrometers  so  that  the  purity  of  the  output  could 
be  quickly  approximated,  the  delivery  of  a  low-grade  drum  of  liquid 
was  rare.  Liquid  testing  considerably  below  95  per  cent  was  returned 
to  the  crude  liquid  storage  tank  and  redistilled. 

The  writers  are  as  yet  undecided  as  to  the  comparative  merits  of 
a  liquid  testing,  say,  95  per  cent  and  one  testing,  say,  98  per  cent  or 
more.  It  is  even  maintained  by  some  fumigators  that  the  high  per- 
centage of  liquid  is  too  volatile  for  safe  handling,  and  that  they  much 
prefer  a  liquid  testing  95  to  96  per  cent.  The  definite  determination 
of  this  point  must  be  made  by  future  investigation.  In  the  present 
state  of  our  knowledge,  it  is  believed  that  a  material  testing  95  per  cent 
or  more  of  hydrocyanic  acid  is  of  a  satisfactory  grade.  The  plant  as 
operating  at  present  is  quite  capable  of  and  does  produce  liquid  of 
this  quality,  or  better,  many  samples  testing  over  98  per  cent. 

Return  Per  Case. — As  the  plant  was  operated  during  the  past 
season  and  based  upon  the  investigation  reported  above,  the  following 
is  believed  to  be  a  fair  return  per  case  of  two  hundred  pounds  of 
sodium  cyanide,  testing  96-98  per  cent  of  sodium  cyanide : 

1.  A  minimum  of  85  pounds  of  absolute  hydrocyanic  acid ;  or 

2.  A  minimum  of  90  pounds  of  liquid  testing  not  less  than  95  per 
cent  hydrocyanic  acid. 

Liquid  of  95  per  cent  purity  should  not  test  less  than  66°  on  the 
Baume  hydrometer  at  a  temperature  of  60°  Fahrenheit,  corresponding 
to  a  specific  gravity  of  .715.  A  gallon  of  liquid  of  this  density  would 
weigh  5.956  pounds. 

The  above  must  not  be  taken  as  final.  As  the  necessary  infor- 
mation is  accumulated  it  is  confidently  anticipated  that  the  yield  in  the 
future  will  be  equal  to  or  even  greater  than  that  now  obtained  from 
the  portable  generators  in  common  use. 

.  Weight  Basis. — Settlements  are  now  made  on  a  basis  of  gallons  of 
liquid  returned  per  case  of  sodium  cyanide  delivered.  The  liquid  can 
be  fairly  easily  measured  when  delivered  to  the  consumer  by  an 
automatic  measuring  device,  but  measuring  of  so  volatile  and  poisonous 


PHYSICAL  AND  CHEMICAL  PROPERTIES  OF  HYDROCYANIC  ACID         411 

a  liquid  without  such  a  device  is  a  rather  dangerous  undertaking 
and  is  not  so  easily  subject  to  accuracy  as  weighing.  It  is  strongly 
urged  that  the  weight  basis  be  adopted  in  transactions  dealing  with 
liquid  hydrocyanic  acid.  The  strongest  argument  in  its  favor  is  that 
the  consumer  would  have  a  ready  and  convenient  means  of  checking 
up  deliveries.  The  weight  of  the  empty  drum  could  be  determined 
and  the  figures  painted  on  the  drum.  The  weighing  of  the  full  drum 
only  requires  a  short  time,  and  in  that  way  the  weight  of  the  liquid 
delivered  would  be  determined  by  deducting  the  weight  of  the  con- 
tainer from  the  gross  weight.  An  additional  argument  in  favor  of 
the  adoption  of  the  weight  basis  in  commercial  transactions  is  evident 
from  the  following:  The  weight  of  the  recovered  liquid  will  be  the 
same  at  any  temperature.  The  corresponding  number  of  gallons, 
however,  will  vary  according  to  the  temperature  of  the  liquid. 

It  has  been  held  by  some  that  the  weight  basis  would  place  the 
consumer  at  a  disadvantage  for  the  reason  that  a  low-grade  liquid 
weighs  considerably  more  than  a  high  grade.  It  is  not  to  be  expected 
that  a  commercial  product  could  be  absolutely  uniform.  If,  however, 
95,  96,  or  some  other  percentage  were  finally  adopted  as  the  minimum 
standard  of  purity,  the  consumer  would  be  justified  in  refusing  any 
material  of  less  purity  than  this.  Fortunately  it  is  unnecessary  to 
have  a  chemical  analysis  made  to  determine  purity.  This  can  be 
determined  accurately  by  observing  specific  gravity  and  temperature 
and  using  the  appended  reference  tables. 

Table  I  following  will  be  of  use  in  making  settlements  for  the 
return  of  liquid,  in  making  dosage  calculations,  etc.  The  figures  in 
the  table  showing  yield  in  gallons  are  correct  when  the  liquid  is 
measured  at  a  temperature  of  15°  C  (60°  F)  only. 


412 


UNIVERSITY   OF    CALIFORNIA — EXPERIMENT   STATION 


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PHYSICAL  AND  CHEMICAL  PROPERTIES  OF  HYDROCYANIC  ACID         413 


PHYSICAL  PROPERTIES 

Miscibility. — During  the  earlier  stages  of  the  commercial  produc- 
tion of  the  liquid  it  was  erroneously  believed  that  mixtures  of  hydro- 
cyanic acid  and  water  would  separate  on  standing  into  layers  of 
different  composition.  The  reason  for  this  belief  was  that  the  first 
run  in  the  morning  was  often  diluted  with  water  remaining  in  the 
condensors  and  conveying  pipes  after  flushing  at  the  end  of  the 
previous  day's  run.  As  soon  as  this  point  was  established  it  became 
the  custom  at  the  plant  to  draw  off  the  first  run  of  low-grade  liquid 
and  return  it  to  the  crude  liquid  receiver  to  be  redistilled. 

It  has  been  determined  that  hydrocyanic  acid  is  miscible  with 
water  in  all  proportions.  When  once  thoroughly  mixed,  the  liquid 
remains  homogeneous  throughout,  except  as  affected  by  chemical  de- 
composition. When  the  two  are  mixed  there  is  always  an  appreciable 
contraction  in  volume  accompanied  by  a  fall  in  temperature.  This 
fact  complicated  the  problem  of  determining  the  relation  of  percentage 
purity  to  specific  gravity  and  necessitated  extensive  experimentation, 
as  will  be  described  under  a  later  heading. 

Evaporation. — The  anhydrous  liquid  has  a  very  strong  affinity  for 
water,  so  if  a  high-grade  liquid  is  exposed  to  moist  air  it  will  either 
absorb  moisture  from  the  air  and  become  dilute  or,  the  acid  being 
more  volatile  than  water,  will  evaporate  at  a  greater  rate,  leaving  a 
residue  of  low-grade  liquid. 

A  cylinder  was  filled  with  a  much  diluted  and  thoroughly  mixed 
sample  of  hydrocyanic  acid.  This  was  analyzed  and  then  the  cylindei' 
was  allowed  to  stand  uncovered  in  an  exposed  place  for  fifteen  hours, 
so  that  evaporation  might  proceed  readily.  In  that  time  about  30 
per  cent  of  the  liquid  had  evaporated.  A  sample  of  the  remaining 
liquid  was  then  analyzed,  and  the  results  were  as  follows: 

Sample  from  cylinder  at  first:  46.6%  hydrocyanic  acid. 

Sample  from  cylinder  after  evaporation:  29.4%  hydrocyanic  acid. 

A  high-grade  liquid  evaporates  so  rapidly  that  its  temperature  is 
lowered  at  times  even  to  the  point  where  particles  of  ice  are  formed. 
In  experimenting  with  the  liquid  in  a  room  where  the  temperature 
was  about  90°  F,  and  in  a  good  current  of  air,  a  cylinder  was  filled 
with  the  liquid  and  enough  more  added  so  as  to  run  down  the  sides 
of  the  cylinder.  The  temperature  of  the  liquid  was  reduced  ten 
degrees  in  ten  minutes.  This  is  a  very  desirable  property,  for  if  the 
liquid  is  warmed  up  to  near  the  boiling  point  and  allowed  to  evaporate 
freely  it  is  automatically  cooled  and  evaporation  thus  retarded. 


414  UNIVERSITY    OF    CALIFORNIA EXPERIMENT   STATION 

Vapor  pressure  has  an  important  bearing  on  the  strength  of 
materials  required  for  containers.  Apparently  the  vapor  pressure 
of  hydrocyanic  acid  is  very  small.  In  other  words,  a  comparatively 
slight  pressure  is  required  to  retain  the  substance  in  a  liquid  state, 
even  at  temperatures  near  its  boiling  point.  The  writers  have  as 
yet  been  unable  to  investigate  this  matter,  but  the  figures  shown  in 
Table  II  are  contributed  through  the  courtesy  of  Mr.  W.  C.  Bass  of 
Los  Angeles  as  being  approximately  correct. 

TABLE  II 
Pressure  of  Hydrocyanic  Acid  (About  97%  HCN)  in  a  Closed  Container  at 

Different  Temperatures 


Temp.  deg.  F 

Pounds  pe 

87 

3.4 

94 

4.9 

100 

7.9 

105 

9.8 

110 

11.8 

115 

13.3 

120 

15.7 

125 

17.7 

SPECIFIC  GRAVITY 

It  is  important  for  the  fumigator  to  know  the  approximate  per- 
centage of  hydrocyanic  acid  in  the  liquid  which  he  uses  in  order  to 
enable  him  to  reject  material  of  low  grade.  This  is  of  special  im- 
portance if  the  weight  basis  be  adopted  in  making  settlement.  The 
sampling  and  analyzing  of  a  poisonous  and  volatile  material  of  this 
sort  presents  unusual  difficulties.  Inasmuch  as  the  density  of  the 
pure  liquid  is  less  than  three-fourths  that  of  water  and  the  principal 
impurities  which  are  apt  to  be  encountered  in  a  commercial  liquid 
are  water  or  other  impurities  which  are  heavier  than  the  pure  liquid, 
it  was  early  recognized  that  the  determination  of  specific  gravity 
might  be  utilized  in  approximating  the  percentage  purity  of  a  com- 
mercial liquid.  This  view  was  confirmed  by  preliminary  experiments 
and  a  hydrometer  spindle  has  been  used  throughout  the  course  of 
these  investigations  as  a  ready  and  satisfactory  means  of  approxi- 
mating purity  of  the  output  of  the  plant. 

The  specific  gravity  of  the  liquid  materially  changes  with  varying 
temperatures.     Also  on  account  of  the  contraction  in  volume  when 


PHYSICAL  AND  CHEMICAL  PROPERTIES  OF  HYDROCYANIC  ACID         415 

water  and  acid  are  mixed  the  rate  of  variation  varies  according  to 
the  percentage  of  water  and  acid  in  the  sample.  These  complications, 
however,  do  not  interfere  with  the  application  of  this  method  of 
approximation,  provided  the  extent  of  these  variations  are  known. 

This  matter  was  gone  into  very  thoroughly  and  data  have  been 
obtained  giving  complete  information  on  all  of  the  points  involved. 
These  data,  presented  in  the  reference  tables  at  the  end  of  this  bulletin, 
were  determined  by  means  of  a  hydrometer  spindle  accurate  to  the 
third  decimal  place.  The  temperature  was  observed  in  degrees  of  the 
Centigrade  scale.  Table  VI  will  indicate  the  percentage  of  absolute 
hydrocyanic  acid  corresponding  to  various  densities  and  at  a  range 
of  temperature  from  5°  to  22°  C.  Hydrometer  spindles  graduated 
in  specific  gravity  are  not  as  readily  obtainable  as  spindles  reading 
in  degrees  Baume.  In  order  to  make  the  tables  available  for  use 
with  a  Baume  hydrometer,  they  have  all  been  recalculated,  indicating 
the  corresponding  Baume  reading  and  the  variation  in  temperature 
according  to  the  Fahrenheit  thermometer.  These  data  are  given  in 
Table  VII. 

These  determinations  were  all  made  upon  the  commercial  liquid. 
The  specific  gravity  at  different  temperatures  of  100  per  cent  material, 
however,  has  been  calculated  from  the  data  for  liquids  of  lower  per- 
centages. It  is  interesting  to  note  that  the  calculated  specific  gravity 
at  18°  C  of  100  per  cent  acid  is  .6943.  The  commonly  accepted 
specific  gravity  of  this  material  is  .6967.^  The  close  agreement  of 
these  two  figures  is  believed  to  be  a  confirmation  of  the  accuracy  of 
the  determinations. 

Thirteen  samples  of  liquid  hydrocyanic  acid  were  selected,  being 
representative  samples  of  the  product  of  the  liquefying  plant  over  a 
period  of  three  months.  Some  were  intentionally  diluted  with  water. 
The  temperature  of  the  samples  was  made  to  vary  and  conditions  so 
arranged  that  they  would  afford  a  fair  measure  of  the  accuracy  of 
the  tables.  The  specific  gravity  and  temperature  of  each  were  care- 
fully observed  and  the  percentage  of  hydrocyanic  acid  determined  by 
reference  to  the  tables,  and  then  by  careful  analysis.  The  results 
are  shown  in  Table  III.  The  laboratory  analysis  is  accurate  to  two- 
tents  of  1  per  cent.  Since  there  is  no  greater  variation  than  the 
experimental  error  between  the  percentages  determined  by  analysis 
and  by  the  tables  and  since  the  conditions  of  the  samples  were  made 
quite  variable,  the  following  table  is  considered  to  be  a  positive  justi- 
fication of  the  tables  and  confirmation  of  their  accuracy. 


3  H.  E.  Williams,  Chemistry  of  Cyanogen  Compounds,  and  their  Manufacture 
and  Estimation.    J.  and  A.  Churchill,  London,  1915. 


Observed 
specific  gravity 

Temperature 
deg.  C 

.736 

17 

.7115 

16 

.704 

16.5 

.7045 

16 

.705 

16 

.704 

16 

.715 

16.5 

.716 

16 

.720 

5.25 

.713 

10 

.7405 

13.5 

.742 

12 

.7185 

14 

HCN 
by  tables 

% 

88.2 

95.6 

97.7 

97.8 

97.7 

97.9 

94.5 

94.4 

97.7 

97.7 

88.1 

88.2 

94.5 

416  UNIVERSITY   OF    CALIFORNIA — EXPERIMENT   STATION 

TABLE  III 

Comparison  of  Eesults  Obtained  on  Determination  of  HCN  by  Using  Our 

Eeference  Tables  and  by  Analysis 

HCN 
by  analysis 

% 

88.2 
95.6 
97.8 
97.9 
97.7 
98.1 
94.7 
94.6 
97.7 
97.7 
88.2 
88.2 
94.7 

Use  of  the  Tables. — The  tables  referred  to  above  make  it  possible 
to  determine  the  quality  of  the  liquid  in  a  moment's  time  by  the  use 
of  a  hydrometer  spindle  graduated  either  in  specific  gravity  or  Baume 
degrees,  taking  into  account  the  temperature  of  the  liquid.  Many 
of  these  spindles  are  provided  with  a  thermometer,  so  that  both 
observations  can  be  made  from  one  instrument.  It  requires  no  tech- 
nical skill  to  make  such  observations.  Any  one  w^ithout  previous 
experience  can  easily  read  the  hydrometer  accurately  v^^ithin  one 
degree  Baume.  This  introduces  an  error  of  approximately  1  per  cent. 
With  a  little  practice  and  with  an  accurately  graduated  instrument 
an  even  closer  approximation  than  this  can  be  made.  After  the 
hydrometer  reading  and  the  temperature  of  the  liquid  have  been 
taken,  the  corresponding  percentage  is  determined  by  referring  to 
Table  VI  if  the  spindle  reads  in  specific  gravity  or  to  Table  VII  if 
the  Baume  hydrometer  has  been  used. 

The  Cyanometer. — The  accumulation  of  the  data  referred  to  above 
has  made  possible  the  construction  of  a  hydrometer  graduated  directly 
in  percentage  hydrocyanic  acid.  The  idea  of  such  an  instrument  is 
not  a  new  one.  In  fact,  alcoholometers,  salometers,  saccharometers, 
etc.,  are  in  common  factory  use  for  the  determination  of  alcohol  in 
mixtures  of  alcohol  and  water,  salt  in  brine,  and  sugar  in  syrup 
respectively.  Our  data  have  made  possible  the  construction  of  a 
''cyanometer"  to  be  used  for  a  purpose  similar  to  the  above.  It  is 
possible  that  the  somewhat  restricted  use  for  these  instruments  might 
not  make  their  construction  attractive  to  instrument  makers.  In  this 
case  the  reference  tables  are  available.    If,  however,  the  idea  appeals 


PHYSICAL  AND  CHEMICAL  PROPERTIES  OP  HYDROCYANIC  ACID         417 

to  the  fumigators  as  of  sufficient  importance  and  the  demand  is  great 
enough,  an  instrument  could  be  procured  which  will  indicate  per- 
centages of  hydrocyanic  acid  directly.  This,  of  course,  should  be 
provided  with  a  thermometer  and  with  a  table  of  temperature  cor- 
rections. All  of  these  data  could  easily  be  contained  within  the  glass 
shell  of  the  average  hydrometer.  A  simplified  scale  for  the  graduation 
of  this  instrument  as  well  as  a  table  for  temperature  correction  is 
shown  below. 


TABLE  IV 

Data  for  Construction  of  the  Cyanometer 

Marked  on  scale 

Corresponding 

marks  on  hydrometers 

Temperatu 

re  corrections 

HCN% 
ateO^F 

Baume  reading 
at  60°  F 

Specific  gravity 
equivalent  to  Baume 

A 

deg.  P 

Corections 

100 

71.0 

.697 

70 

-2% 

99 

69.8 

.701 

65 

-1% 

98 

68.7 

.705 

60 

0 

97 

67.8 

.708 

55 

+  1% 

96 

66.9 

.711 

50 

+2% 

95 

65.9 

.715 

45 

+3% 

94 

65.0 

.718 

40 

+4% 

93 

64.1 

.72] 

92 

63.2 

.725 

91 

62.3 

.728 

90 

61.4 

.732 

89 

60.6 

.735 

88 

59.7 

.738 

87 

58.8 

.742 

86 

58.0 

.745 

85 

57.1 

.748 

An  instrument  of  this  kind  is  commonly  calibrated  for  use  at  a 
temperature  of  60°  F,  and  is  correct  at  that  temperature  only.  If 
used  at  any  other  temperature  than  the  above  the  observed  reading 
should  be  corrected  according  to  the  variation  above  or  below  the 
temperature  at  which  the  instrument  is  calibrated. 


CHEMICAL  PROPERTIES 

Hydrocyanic  Acid;  Priissic  Acid 

Chemical  Symbol,  HON;  Molecular  Weight,  27.02 

DECOMPOSITION 

Most  impurities  tend  to  accelerate  the  decomposition  of  hydro- 
cyanic acid.  The  purer  the  liquid  is  the  better  its  keeping  qualities. 
Impurities  may  be  present  especially  from  contact  with  metals  or  in 


418  UNIVERSITY   OF    CALIFORNIA — EXPERIMENT   STATION 

the  form  of  other  products.  These  may  have  their  origin  in  the  manu- 
facturing plant  or  in  the  containers  used  for  handling  and  dispensing 
the  liquid.  Some  metals  react  with  the  liquid  and  the  metallic  cyan- 
ides thus  formed  may  later  be  precipitated,  forming  a  troublesome 
sediment.  In  some  cases  they  can  be  easily  removed  by  straining. 
Some  of  the  causes  of  decomposition  are  solely  under  the  control  of 
the  manufacturer,  while  others  are  under  the  control  of  the  fumigator. 
"When  the  liquid  decomposes  it  forms  several  substances  which 
themselves  accelerate  decomposition  of  fresh  liquid  with  which  they 
come  in  contact.  In  other  words,  decomposition  appears  to  be  a 
cumulative  process.  Undesirable  impurities  may  be  imperceptible  in 
a  freshly  prepared  liquid,  but  nevertheless  have  their  effect.  The 
decomposition  is  gradual  at  first  and  is  marked  with  the  appearance 
of  a  faint  yellow  tint  and  an  accompanying  lowering  of  percentage 
of  hydrocyanic  acid.  As  this  proceeds  the  color  becomes  deeper  and 
merges  into  brown,  when  the  chemical  changes  take  place  more  rapidly 
and  new  gases  are  formed  in  great  quantity.  At  this  stage  a  dark 
brown  or  black  flaky  precipitate  is  formed.  After  complete  decom- 
position the  newly  formed  gases  have  escaped,  leaving  a  bulky,  black 
sediment  much  resembling  carbon,  or,  if  the  liquid  is  confined,  the 
pressure  of  these  gases  is  oftentimes  sufficient  to  burst  the  container. 
The  above  description  is  well  illustrated  by  the  following  record  of 
a  decomposed  sample.  Table  V. 

TABLE  V 
Record  of  a  Decomposed  Sample 

%  HON 

94.7 
93.8 
93.2 
93.2 
93.3 
92.8 
92.3 
92.3 
90.2 
80.0 

Warning  Signs. — So  far  as  observed,  when  a  sample  starts  to  de- 
teriorate a  color  of  some  sort,  usually  yellow,  is  always  formed.  Am- 
monia seems  to  be  one  of  the  gases  formed  in  greatest  quantity,  or  at 
least  one  which  can  most  readily  be  detected  in  decomposing  hydro- 
cyanic acid.  The  formation  of  any  color  or  an  odor  of  ammonia  then 
may  be  taken  as  a  warning. 


Analysis 

Date,  1918 

Color  of  sample 

Weather 

1 

Oct. 

Straw  color 

warm 

2 

4 

Amber 

warm 

3 

8 

Amber 

warm 

4 

14 

Amber 

cool 

5 

16 

Amber 

cool 

6 

21 

Yellow 

cool 

7 

25 

Yellower 

cool 

8 

29 

Very  yellow     • 

•  cool 

9 

^  ov.  2 

Brownish  yellow 

warm 

10 

4 

Black  sludge 

cool 

PHYSICAL  AND  CHEMICAL  PROPERTIES  OF  HYDROCYANIC  ACID         419 

Keeping  Qualities. — The  question  has  often  been  asked,  how  long 
the  liquid  will  keep.  This  question  cannot  be  answered  easily.  Some 
samples  several  years  old  are  apparently  as  good  now  as  when  first 
prepared.  Other  samples  decomposed  completely  within  a  few  days 
or  weeks.  One  apparently  good  sample  which  was  closely  observed 
completely  decomposed  in  forty  days.  Another  sample  of  similar  ap- 
pearance and  kept  under  the  same  conditions  was  as  good  at  the  end 
of  four  months  as  it  was  at  first.  The  natural  life  of  the  liquid  de- 
pends upon  its  history  in  the  course  of  manufacture  as  well  as  upon 

conditions  of  handling  and  storage.     Some  of  the  factors  influ- 
encing the  keeping  qualities  of  the  liquid  are  discussed  below. 

Dilution. — Our  experiments  point  toward  the  conclusion  that  the 
presence  of  water,  especially  in  amounts  more  than  5  per  cent,  are 
favorable  to  decomposition  and  tend  to  increase  the  effect  of  the  acid 
upon  many  metals.  It  is  probable  that  a  liquid  as  nearly  anhydrous 
as  could  be  produced  would  be  the  most  desirable  from  these  stand- 
points. The  great  volatility  of  a  liquid  of  this  nature,  however,  may 
necessitate  a  compromise  between  the  highest  purity  obtainable  and 
one  more  convenient  to  handle. 

Temperature. — The  liquid  resists  decomposition  much  better  at  low 
temperatures,  other  conditions  being  the  same,  than  it  does  at  high 
temperatures.  If  held  in  an  open  container  it  would  boil  at  a  tem- 
perature of  about  80°  F.  The  liquid  should  be  kept  cool  at  all  tinies, 
preferably  never  becoming  warmer  than  60°  F.  If  the  liquid  is 
allowed  to  become  sufficiently  warm,  it  is  very  easy  to  see  that  a  closed 
drum  of  liquid  could  be  burst  (see  Table  II).  Some  of  the  explosions 
of  previous  years  may  be  partly  accounted  for  from  this  cause,  as  well 
as  from  the  decomposition  of  the  liquid  producing  gases  of  greater 
vapor  pressure  than  hydrocyanic  acid. 

Decomposition  Residue. — The  dark  colored  deposit  from  a  partly 
decomposed  sample  has  been  demonstrated  to  be  highly  favorable  to 
decomposition  when  placed  in  a  fresh  sample.  This  matter  has  an 
important  bearing  on  the  washing  out  of  delivery  containers,  atomizing 
machinery  and  any  other  vessels  used  in  storage  or  handling.  Invest- 
igations are  under  way  in  an  effort  to  disclose  some  substance  which 
can  be  used  to  change  the  nature  of  this  deposit  so  that  it  would  not 
be  so  favorable  to  decomposition.  Sufficient  progress  has  not  been 
made  to  warrant  publication. 

A  portion  of  the  black  solid  residue  remaining  after  a  sample  of 
hydrocyanic  acid  had  completely  decomposed  was  spread  out  and  left 
exposed  to  the  air  for  three  weeks.  At  the  end  of  that  time  some  of 
this  solid,  resembling  charcoal  in  appearance,  was  added  to  some  hydro- 


420  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

cyanic  acid  in  a  small  flask  and  set  away.  The  liquid  became  slightly 
yellow  as  soon  as  the  material  had  settled.  Within  one  day  the  liquid 
was  brownish  yellow ;  in  four  days,  brown  and  throwing  down  a  de- 
posit ;  within  two  weeks,  the  liquid  had  completely  decomposed.  The 
same  lot  of  liquid  without  the  addition  of  decomposition  residue 
remained  unimpaired  for  several  months. 

Some  of  the  black  deposit  being  thrown  down  from  a  decomposing 
sample  was  filtered  from  the  liquid  and  added  to  a  fresh  portion  of 
clear  liquid  and  then  set  away.  The  effect  was  in  all  respects  the 
same  as  described  above,  except  that  the  chemical  action  was  consid- 
erably slower.  In  four  days  the  liquid  had  become  bright  lemon 
yellow ;  in  two  weeks,  brown ;  and  in  five  weeks  had  completely  de- 
composed. 

Alkalies. — It  has  been  long  known  that  alkalies  are  favorable  to 
decomposition.  This  has  been  confirmed  in  our  investigations  using 
sodium,  potassium,  and  ammonium  hydroxides.  Ammonia  was  found 
to  be  the  most  energetic. 

Acids. — Sulfuric  acid  and  hydrochloric  acid  even  when  used  in 
large  amounts  do  not  appear  to  affect  the  liquid  seriously.  Nitric  acid, 
however,  has  a  very  serious  influence. 

Sodium  Cyanide. — The  undesirable  effect  of  sodium  cyanide  is 
equal  to  or  even  greater  than  the  alkalies  mentioned  above. 

Soap. — Several  varieties  of  soap  were  found  to  decompose  the  liquid 
very  rapidly.  Doubtless  this  is  due  to  the  presence  of  alkali  or  to 
hydrolysis  of  alkali  salts. 

Packing  Materials. — Quite  a  variety  of  the  more  common  packing 
materials — pure  rubber,  red  rubber,  white  rubber,  leather,  "garlock", 
an  asbestos  packing,  and  an  asphalt  canvas  packing — were  experi- 
mented with.  So  far  as  we  were  able  to  observe,  there  is  nothing 
dangerous  about  any  of  these  ordinary  materials  used  for  packing  so 
far  as  the  decomposing  effect  on  hydrocyanic  acid  is  concerned. 
Rubber  does  not  appear  to  affect  the  liquid,  but  the  rubber  itself  is 
sooner  or  later  destroyed. 

Metals. — Some  metals  are  attacked  by  the  acid.  On  the  other 
hand,  some  metals  seem  to  act  as  catalytic  agents  and  promote  a  rapid 
decomposition  of  the  acid.  Others  apparently  have  no  effect  what- 
ever. The  metals  appearing  to  act  upon  the  acid  more  energetically 
are :  lead,  com,mercial  tin,  solder,  cast  iron,  and  steel.  These  metals 
very  clearly  should  be  avoided  in  the  construction  of  liquefying  plants 
and  in  delivery  containers,  atomizing  machinery,  fittings,  etc. 


PHYSICAL  AND  CHEMICAL  PROPERTIES  OF  HYDROCYANIC  ACID         421 


ACTION  ON  METALS 
A  series  of  experiments  was  made  to  test  the  action  of  liquid 
hydrocyanic  acid  on  various  metals,  the  object  being  to  obtain  data 
for  the  intelligent  selection  of  materials  for  the  construction  of  de- 
livery containers,  atomizing  apparatus,  condensers  and  other  equip- 
ment for  use  in  connection  with  the  new  industry. 

Small  pieces  of  various  metals,  solid  and  plated,  were  first  weighed 
and  then  sealed  in  glass  tubes  containing  a  small  quantity  of  liquid 
hydrocyanic  acid.  The  amount  of  liquid  was  regulated  so  that  only 
a  part  of  the  metals  was  exposed  to  the  liquid  while  the  remainder 
was  exposed  to  the  vapors.  These  specimens  have  been  under  obser- 
vation for  four  months  and  would  all  have  furnished  fairly  complete 
data  on  the  action  of  the  acid  on  the  commoner  metallic  substances 
except  for  the  recent  suspicion  that  the  glass  itself  may  have  been 
responsible  for  the  decomposition  of  the  liquid. 

Our  experiments  have  shown  that  certain  kinds  of  glass  under 
some  conditions  appear  to  cause  the  decomposition  of  liquid  hydro- 
cyanic acid.  So  far  as  we  are  able  to  determine,  boro-silicate  glass 
does  not  affect  the  liquid.  The  experiments  are  therefore  being  re- 
peated, using  this  kind  of  glassware  for  the  test  containers.  A  large 
variety  of  metals  and  various  enamels  and  varnishes  are  also  being 
tested.  The  complete  results  of  these  experiments,  however,  will  not 
be  available  for  the  coming  fumigating  season. 

Resistant  Metals. — Notwithstanding  the  possible  combined  influence 
of  metal  and  glass  upon  liquid  hydrocyanic  acid,  a  few  metals  have 
not  been  affected  by  four  months'  contact  with  prussic  acid.  Alumi- 
num, block  tin,  and  pure  zinc  apparently  are  not  changed  in  the  least 
and  the  liquid  in  contact  with  them  is  as  clear  and  colorless  as  when 
first  sealed  up.  The  liquid  on  the  brass,  nickel,  and  silver  has  become 
slightly  yellow ;  that  on  the  copper  is  still  good,  but  the  copper  has  a 
somewhat  roughened  appearance  as  if  it  had  been  slightly  acted  upon. 

While  pure  zinc  noted  above  is  apparently  quite  resistant  to  the 
action  of  prussic  acid,  a  piece  of  plumbers'  ordinary  sheet  zinc  was 
soon  covered  with  a  white  coating  and  a  considerable  quantity  of 
white  sediment  was  deposited  in  the  liquid.  The  liquid  itself  remained 
colorless  and  apparently  unaffected  throughout  the  experiment. 

Delivery  Druyns. — Judging  from  the  experiments  described  above 
and  from  a  consideration  of  the  cost  and  properties  of  the  various 
materials  observed,  aluminum  is  the  most  promising  material  for 
the  construction  of  delivery  drums.  Brass  fittings  appear  to  be  per- 
missible. 


422  UNIVERSITY   OF    CALIFORNIA EXPERIMENT   STATION 


SUMMARY 

The  ready  acceptance,  by  fumigators,  of  liquid  hydrocyanic  acid 
as  a  new  convenience  in  citrus  fumigation  has  resulted  in  a  study  of 
the  physical  and  chemical  properties  of  the  liquid. 

Two  test  runs  of  the  liquefying  plant  were  made  in  order  to  estab- 
lish a  basis  of  settlement  between  plant  and  fumigator.  The  liquid 
hydrocyanic  acid  recovered  in  the  first  test  run  was  80.1  per  cent  of 
the  greatest  possible  yield ;  in  the  second,  76.3  per  cent ;  an  average 
of  78.2  per  cent. 

The  average  purity  of  the  liquid  obtained  in  the  first  run  was 
97.57  per  cent ;  in  the  second,  94.27  per  cent. 

The  average  purity  of  the  liquid  delivered  during  the  past  fumi- 
gating season  w^as  above  95  per  cent  absolute  hydrocyanic  acid. 
Material  of  95  per  cent  or  greater  purity  is  considered  of  a  satisfac- 
tory grade. 

As  the  plant  was  operated  last  season,  the  following  is  believed 
to  be  a  fair  return  per  case  of  two  hundred  pounds  of  sodium  cyanide : 

1.  A  minimum  of  85  pounds  of  absolute  hydrocyanic  acid;  or 

2.  A  minimum  of  90  pounds  of  liquid  testing  not  less  than  95  per 
cent  purity. 

As  the  necessary  information  is  accumulated  it  is  confidently  an- 
ticipated that  the  yield  in  tbe  future  will  be  equal  to  or  even  greater 
than  that  now  obtained  from  the  portable  generators  in  common  use. 

The  weight  basis  for  commercial  transactions  is  strongly  urged  for 
adoption  in  preference  to  the  volume  basis  now  in  use.  Deliveries 
could  be  more  easily  checked  up  by  weighing  than  by  measuring,  and 
this  is  also  less  dangerous.  Furthermore,  the  weight  of  the  recovered 
liquid  will  be  the  same  at  any  temperature,  while  the  corresponding 
number  of  gallons  will  vary  according  to  the  temperature  at  which 
it  is  measured. 

A  table  has  been  prepared  showing  the  weights  and  corresponding 
volumes  of  various  grades  of  commercial  liquid  and  the  quantities 
thereof  corresponding  to  various  percentages  of  the  maximum  yield 
(Table  I). 

It  has  been  determined  that  the  acid  is  miscible  with  water  in  all 
proportions  and  will  not  stratify  upon  standing. 

Hydrocyanic  acid  evaporates  more  rapidly  than  water  from  dilute 
mixtures  of  the  two. 

Complete  data  have  been  obtained  on  the  specific  gravity  of  com- 
mercial liquid  hydrocyanic  acid  testing  from  70  per  cent  to  100  per 


PHYSICAL  AND  CHEMICAL  PROPERTIES  OF  HYDROCYANIC  ACID         423 

cent  purity,  and  upon  the  extent  of  variation  of  hydrometer  readings 
as  affected  by  temperature.  These  figures  are  presented  in  the  form 
of  reference  tables  at  the  end  of  the  bulletin.  These  tables  make  it 
possible  to  determine  the  quality  of  a  liquid  in  a  moment's  time  by 
the  use  of  a  hydrometer  graduated  either  in  specific  gravity  or  Baume 
degrees. 

The  accumulation  of  the  data  referred  to  above  has  made  possible 
the  construction  of  a  cyanometer,  a  hydrometer  graduated  directly  in 
percentages  of  hydrocyanic  acid  and  provided  with  a  simple  table  of 
temperature  corrections. 

A  method  of  analysis  has  been  selected  and  shown  to  give  concord- 
ant results  within  two-tenths  of  1  per  cent. 

The  development  of  any  color,  usually  yellow,  or  an  odor  of  am- 
monia may  be  taken  as  a  warning  of  incipient  decomposition  of  the 
liquid. 

Factors  and  materials  favoring  decomposition  are :  water  in  excess 
of  5  per  cent ;  high  temperatures ;  residue  from  a  decomposed  liquid ; 
all  alkalies,  nitric  acid,  sodium  cyanide ;  soap ;  or  contact  with  lead, 
commercial  tin,  impure  zinc,  solder,  cast  iron,  or  steel. 

The  following  metals  were  found  to  be  highly  resistant  to  the  acid, 
somewhat  in  the  order  named :  aluminum,  block  tin,  pure  zinc,  brass, 
nickel,  silver,  and  copper. 

Aluminum  is  the  most  promising  material  for  the  construction  of 
delivery  drums.    Brass  fittings  are  permissible. 


REFERENCE  TABLES 

The  following  reference  tables  and  their  use  in  determining  the 
percentage  of  absolute  hydrocyanic  acid  in  commercial  liquid  hydro- 
cyanic acid  have  been  discussed  under  the  heading  ' '  Specific  Gravity ' ' 
in  the  section  on  physical  properties. 


424 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT   STATION 


TABLE  VI 

For  Use  With  Specific  Gravity  Hydrometer 
Calibrated  at  15°  C 


Observed  Temperature  °  C 


Observed 

Specific 

22 

21 

20 

19 

18 

17 

16 

15 

14 

Gravity 

Corresponding  Percent,  l 

Hydrocy; 

anic  Acid 

.690 

99.7 

.692 

99.1 

99.5 

99.9 

.694 

98.5 

98.9 

99.3 

99.7 

.696 

97.9 

98.3 

98.7 

99.1 

99.5 

99.9 

.698 

97.3 

97.7 

98.1 

98.5 

98.9 

99.3 

99.7 

100 

.700 

96.7 

97.1 

97.5 

97.9 

98.3 

98.7 

99.1 

99.6 

100 

.702 

96.1 

96.5 

96.9 

97.3 

97.7 

98.1 

98.5 

98.9 

99.4 

.704 

95.5 

95.9 

96.3 

96.7 

97.1 

97.5 

97.9 

98.4 

98.8 

.706 

94.9 

95.3 

95.7 

96.1 

96.5 

96.9 

97.3 

97.8 

98.2 

.708 

94.3 

94.7 

95.1 

95.5 

95.9 

96.3 

96.7 

97.1 

97.6 

.710 

93.7 

94.1 

94.5 

94.9 

95.3 

95.7 

96.1 

96.5 

97.0 

.712 

93.1 

93.5 

93.9 

94.3 

94.7 

95.1 

95.5 

95.9 

96.4 

.714 

92.6 

93.0 

93.4 

93.8 

94.2 

94.6 

95.0 

95.3 

95.8 

.716 

92.0 

92.4 

92.8 

93.2 

93.6 

94.0 

94.4 

94.7 

95.2 

.718 

91.4 

91.8 

92.2 

92.6 

93.0 

93.4 

93.8 

94.1 

94.6 

.720 

90.8 

91.2 

91.6 

92.0 

92.4 

92.8 

93.2 

93.6 

94.0 

.722 

90.2 

90.6 

91.0 

91.4 

91.8 

92.2 

92.6 

93.0 

93.4 

.724 

89.6 

90.0 

90.4 

90.8 

91.2 

91.6 

92.0 

92.4 

92.8 

.726 

89.0 

89.4 

89.8 

90.2 

90.6 

91.0 

91.4 

91.8 

92.2 

.728 

88.5 

88.9 

89.3 

89.7 

90.1 

90.5 

90.9 

91.2 

91.6 

.730 

87.9 

88.3 

88.7 

89.1 

89.5 

89.9 

90.3 

90.6 

91.0 

.732 

87.3 

87.7 

88.1 

88.5 

88.9 

89.3 

89.7 

90.0 

90.4 

.734 

86.7 

87.1 

87.5 

87.9 

88.3 

88.7 

89.1 

89.4 

89.8 

.736 

86.2 

86.5 

87.0 

87.4 

87.8 

88.2 

88.6 

88.8 

89.2 

.738 

85.6 

86.0 

86.4 

86.8 

87.2 

87.5 

87.9 

88.2 

88.6 

.740 

85.0 

85.4 

85.8 

86.2 

86.6 

86.9 

87.3 

87.6 

88.0 

.742 

84.4 

84.8 

85.2 

85.6 

86.0 

86.3 

86.7 

87.0 

87.4 

.744 

83.8 

84.2 

84.6 

85.0 

85.4 

85.7 

86.1 

86.4 

86.8 

.746 

83.3 

83.7 

84.1 

84.5 

84.8 

85.1 

85.5 

85.8 

86.2 

.748 

82.7 

83.1 

83.5 

83.9 

84.2 

84.5 

84.9 

85.2 

85.6 

.750 

82.1 

82.5 

82.9 

83.3 

83.6 

83.9 

84.3 

84.6 

85.0 

.  752 

81.6 

82.0 

82.4 

82.7 

83.0 

83.3 

83.6 

84.0 

84.4 

.754 

81.0 

81.4 

81.8 

82.1 

82.4 

82.7 

83.1 

83.5 

83.8 

.756 

80.4 

80.8 

81.2 

81.5 

81.8 

82.1 

82.5 

82.9 

83.2 

PHYSICAL  AND  CHEMICAL  PROPERTIES  OF  HYDROCYANIC  ACID 


425 


Observed 
Specific 
Gravity 


.690 
.692 
.694 
.69) 
.698 

.700 
.702 
.704 
.706 
.708 

.710 
.712 
.714 
.716 

.718 

.720 

,722 

.724 

726 

.728 

,730 
,732 
,734 
,736 

,738 

,740 
,742 

,744 
,746 
,748 

.750 
,752 
.754 
,756 


TABLE  VI  (Continued) 
For  Use  With  Specific  Gravity  Hydrometer 
Calibrated  at  15°  C 


13 


12 


Observed  Temperature  °  C 
11  10  9  8  7 

Corresponding  Percent.  Hydrocyanic  Acid 


6 


99.8 

........ 

99.2 

99.6 

100 

98.6 

99.0 

99.4 

99.8 

98.0 

98.4 

98.8 

99.2 

99.6 

100 



97.4 

97.8 

98.2 

98.6 

99.0 

99.4 

99.9 

96.8 

97.2 

97.6 

98.0 

98.4 

98.8 

99.3 

99.7 

96.2 

96.6 

97.0 

97.4 

97.8 

98.2 

98.7 

99.1 

99.6 

95.6 

96.0 

96.4 

96.7 

97.2 

97.6 

98.1 

98.5 

99.0 

95.0 

95.4 

95.8 

96.1 

96.6 

97.0 

97.5 

97.9 

98.4 

94.4 

94.8 

95.2 

95.5 

96.0 

96.4 

96.9 

97.3 

97.8 

93.8 

94.2 

94.5 

94.9 

95.3 

95.8 

96.2 

96.6 

97.1 

93.2 

93.6 

93.9 

94.3 

94.7 

95.1 

95.6 

96.0 

96.5 

92.6 

93.0 

93.3 

93.7 

94.1 

94.5 

95.0 

95.4 

95.9 

92.0 

92.4 

92.8 

93.1 

93.5 

93.9 

94.3 

94.7 

95.3 

91.4 

91.8 

92.2 

92.5 

92.9 

93.3 

93.7 

94.1 

94.7 

90.8 

91.2 

91.6 

91.9 

92.3 

92.7 

93.1 

93.5 

94.0 

90.2 

90.6 

91.0 

91.3 

91.7 

92.1 

92.5 

92.9 

93.4 

89.6 

90.0 

90.4 

90.7 

91.1 

91.5 

91.9 

92.3 

92.8 

89.0 

89.4 

89.8 

90.1 

90.5 

90.9 

91.3 

91.7 

92.2 

88.4 

88.8 

89.2 

89.5 

89.9 

90.3 

90.7 

91.1 

91.6 

87.8 

88.2 

88.6 

88.9 

89.3 

89.7 

90.1 

90.5 

91.0 

87.2 

87.6 

88.0 

88.3 

88.7 

89.1 

89.5 

89.9 

90.4 

86.6 

87.0 

87.4 

87.7 

88.1 

88.5 

88.9 

89.3 

89.8 

86.0 

86.4 

86.8 

87.1 

87.5 

87.9 

88.3 

88.7 

89.1 

85.4 

85.8 

86. 2 

86.5 

86.9 

87.3 

87.7 

88.1 

88.5 

84.8 

85.2 

85.6 

85.9 

86.3 

86.7 

87.1 

87.5 

87.9 

84.2 

84.6 

85.0 

85.3 

85.7 

86.1 

86.5 

86.9 

87.3 

83.6 

84.0 

84.4 

84.7 

85.1 

85.5 

85.9 

86.3 

86.7 

426 


UNIVERSITY   OF    CALIFORNIA EXPERIMENT    STATION 


TABLE  VII 

For  Use  With  Baume  Hydrometer 

Calibrated  at  60°F. 


Observed  Temperature  °F. 


Observed 

Degrees 

70 

69 

68 

67 

66 

65 

64 

63 

62 

61 

60 

Baume. 

Corresponding  Percent.  ; 

Hydrocyanic  Acid 

72.5 

99.7 

100 

72.0 

99.1 

99.3 

99.5 

99.7 

99.9 

71.5 

98.6 

98.8 

99.0 

99.2 

99.4 

99.7 

100 



71.0 

98.1 

98.3 

98.6 

98.8 

99.0 

99.2 

99.4 

99.6 

99.8 

100 

, 

70.5 

97.6 

97.8 

98.0 

98.2 

98.4 

98.6 

98.8 

99.1 

99.3 

99.5 

99.7 

70.0 

97.1 

97.3 

97.5 

97.7 

98.0 

98.2 

98.4 

98.7 

98.9 

99.1 

99.3 

69.5 

96.6 

96.8 

97.0 

97.2 

97.4 

97.6 

97.8 

98.0 

98.2 

98.4 

98.7 

69.0 

96.1 

96.3 

96.5 

96.7 

97.0 

97.2 

97.4 

07.6 

97.8 

98.1 

98.3 

68.5 

95.5 

95.7 

95.9 

96.1 

96.4 

96.6 

96.9 

97.1 

97.3 

97.6 

97.8 

68.0 

95.0 

95.2 

95.4 

95.6 

95.9 

96.1 

96.3 

96.5 

96.8 

97.0 

97.2 

67.5 

94.4 

94.6 

94.8 

95.0 

95.3 

95.5 

95.7 

95.9 

96.1 

96.4 

96.6 

67.0 

93.9 

94.1 

94.3 

94.5 

94.8 

95.0 

95.2 

95.4 

95.6 

95.9 

96.1 

66.5 

93.4 

93.6 

93.8 

94.0 

94.3 

94.5 

94.7 

94.9 

95.2 

95.4 

95.6 

66.0 

92.9 

93.1 

93.3 

93.5 

93.7 

94.0 

94.2 

94.4 

94.6 

94.9 

95.1 

65.5 

92.4 

92.6 

92.8 

93.0 

93.2 

93.5 

93.7 

93.9 

94.1 

94.3 

94.5 

65.0 

91.8 

92.0 

92.2 

92.4 

92.6 

92.8 

93.1 

93.3 

93.5 

93.7 

93.9 

64.5 

91.2 

91.4 

91.6 

91.8 

92.1 

92.3 

92.5 

92.7 

92.9 

93.2 

93.4 

64.0 

90.7 

90.9 

91.1 

91.3 

91.6 

91.8 

92.0 

92.2 

92.4 

92.7 

92.9 

63.5 

90.1 

90.3 

90.5 

90.7 

90.9 

91.2 

91.4 

91.6 

91.8 

92.1 

92.3 

63.0 

89.6 

89.8 

90.0 

90.2 

90.5 

90.7 

90.9 

91.1 

91.4 

91.6 

91.8 

62.5 

89.1 

89.3 

89.5 

89.7 

89.9 

90.2 

90.4 

90.6 

90.8 

91.0 

91.2 

62.0 

88.5 

88.7 

88.9 

89.1 

89.3 

89.6 

89.8 

90.0 

90.2 

90.4 

90.6 

61.5 

88.0 

88.2 

88.4 

88.6 

88.8 

89.0 

89.3 

89.5 

89.7 

89.9 

90.1 

61.0 

87.3 

87.5 

87.7 

87.9 

88.1 

88.3 

88.6 

88.8 

89.0 

89.2 

89.4 

60.5 

86.8 

87.0 

87.2 

87.4 

87.6 

87.8 

88.0 

88.3 

88.5 

88.7 

88.9 

60.0 

86.3 

86.5 

86.7 

86.9 

87.1 

87.4 

87.6 

87.8 

88.0 

88.2 

88.4 

59.5 

85.8 

86.0 

86.2 

86.4 

86.6 

86.8 

87.0 

87.2 

87.4 

87.6 

87.8 

59.0 

85.2 

85.4 

85.6 

85.8 

86.0 

86.2 

86.4 

86.6 

86.8 

87.0 

87.2 

58.5 

84.6 

84.8 

85.0 

85.2 

85.4 

85.6 

85.8 

86.0 

86.2 

86.4 

86.6 

58.0 

84.0 

84.2 

84.4 

84.6 

84.8 

85.0 

85.2 

85.4 

85.6 

85.8 

86.0 

57.5 

83.5 

83.7 

83.9 

84.1 

84.3 

84.5 

84.7 

84.9 

85.1 

85.3 

85.5 

57.0 

82.9 

83.1 

83.3 

83.5 

83.7 

83.9 

84.1 

84.3 

84.5 

84.7 

84.9 

56.0 

82.3 

82.5 

82.7 

82.9 

83.1 

83.3 

83.5 

83.7 

83.9 

84.1 

84.3 

PHYSICAL  AND  CHEMICAL  PROPERTIES  OF  HYDROCYANIC  ACID 


427 


TABLE  VII  (Continued) 

For  Use  With  Baume  Hydrometer 
Calibrated  at  60°F. 


Observed  Temperature  °F. 


Observed 

Degrees 

59 

58 

57 

56 

55 

54 

53 

52 

51 

50 

Baume 

Corresponding 

;  Percent.  Hydrocyanic  Acid 

72.5 

72.0 

71.5 

71.0 

70.5 

100 

70.0 

99.6 

99.8 

100 

69.5 

99.0 

99.2 

99.4 

99.6 

99.8 

100 

69.0 

98.5 

98.7 

98.9 

99.1 

99.3 

99.5 

99.8 

100 

68.5 

98.0 

98.2 

98.4 

98.6 

98.8 

99.0 

99.3 

99.5 

99.7 

100 

68.0 

97.4 

97.6 

97.8 

98.1 

98.3 

98.5 

98.8 

99.0 

99.2 

99.5 

67.5 

96.9 

97.1 

97.3 

97.5 

97.8 

98.0 

98.2 

98.4 

98.6 

98.9 

67.0 

96.3 

96.5 

96.8 

97.0 

97.2 

97.5 

97.7 

97.9 

98.1 

98.4 

66.5 

95.8 

96.0 

96.3 

96.5 

96.7 

96.9 

97.1 

97.4 

97.6 

97.8 

66.0 

95.3 

95.5 

95.7 

96.0 

96.2 

96.4 

96.6 

96.9 

97.1 

97.3 

65.5 

94.7 

95.0 

95.2 

95.4 

95.6 

95.9 

96.1 

96.3 

96.5 

96.7 

65.0 

94.1 

94.4 

94.6 

94.8 

95.0 

95.3 

95.5 

95.7 

95.9 

96.1 

64.5 

93.6 

93.8 

94.0 

94.3 

94.5 

94.7 

94.9 

95.1 

95.3 

95.5 

64.0 

93.1 

93.3 

93.5 

93.7 

94.0 

94.2 

94.4 

94.6 

94.8 

95.0 

63.5 

92.5 

92.7 

92.9 

93.1 

93.4 

93.6 

93.8 

94.0 

94.2 

94.4 

63.0 

92.0 

92.2 

92.4 

92.6 

92.9 

93.1 

93.3 

93.5 

93.7 

93.9 

62.5 

91.4 

91.7 

91.9 

92.1 

92.3 

92.5 

92.7 

92.9 

93.1 

93.3 

62.0 

90.8 

91.0 

91.3 

91.5 

91.7 

91.9 

92.1 

92.3 

92.5 

92.7 

61.5 

90.3 

90.5 

90.7 

90.9 

91.1 

91.3 

91.5 

91.8 

92.0 

92.2 

61.0 

89.6 

89.8 

90.0 

90.4 

90.5 

90.7 

90.9 

91.2 

91.4 

91.6 

60.5 

89.1 

89.3 

89.5 

89.8 

90.0 

90.2 

90.4 

90.6 

90.8 

91.0 

60.0 

88.6 

88.8 

89.0 

89.3 

89.5 

89.7 

89.9 

90.1 

90.3 

90.5 

59.5 

88.0 

88.3 

88.5 

88.7 

88.9 

89.1 

89.3 

89.5 

89.7 

89.9 

59.0 

87.4 

87.6 

87.9 

88.1 

88.3 

88.5 

88.7 

88.9 

89.1 

89.3 

58.5 

86.8 

87.0 

87.3 

87.5 

87.7 

87.9 

88.1 

88.3 

88.5 

88.7 

58.0 

86.2 

86.5 

86.7 

86.9 

87.1 

87.3 

87.5 

87.7 

87.9 

88.1 

57.5 

85.7 

85.9 

86.1 

86.3 

86.5 

86.7 

86.9 

87.1 

87.3 

87.5 

57.0 

85.1 

85.3 

85.5 

85.7 

85.9 

86.1 

86.3 

86.5 

86.7 

86.9 

56.5 

84.5 

84.7 

84.9 

85.1 

85.3 

85.5 

85.7 

85.9 

86.1 

86.3 

428 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


TABLE  VII  {Concluded) 

For  Use  With  Baume  Hydrometer 
Calibrated  at  60°F. 


Observed  Temperature  °F. 


Observed 

Degrees 

49 

48 

47 

46 

45 

44 

43 

42 

41 

40 

Baume 

Corresponding 

;  Percent.  Hydrocyanic 

Acid 

72.-5 

72.0 

71.5 

71.0 

70.5 

70.0 

69.5 

69.0 

68.5 

68.0 

99.7 

10) 

67.5 

99.1 

99.4 

99.6 

99.9 

67.0 

98.6 

98.8 

99.1 

99.3 

99.6 

99.8 

100 

66.5 

98.0 

98.3 

98.5 

98.7 

99.0 

99.2 

99.4 

99.6 

99.8 

100 

66.0 

97.5 

97.8 

98.0 

98.3 

98.5 

98.7 

98.9 

99.1 

99.3 

99.5 

65.5 

97.0 

97.2 

97.5 

97.7 

98.0 

98.2 

98.4 

98.6 

98.9 

99.1 

65.0 

96.4 

96.6 

96.9 

97.2 

97.4 

97.7 

97.9 

98.1 

98.4 

98.6 

64.5 

95.8 

96.0 

96.3 

96.6 

96.8 

97.1 

97.3 

97.6 

97.8 

98.1 

64.0 

95.3 

95.5 

95.8 

96.0 

96.3 

96.5 

96.8 

97.0 

97.2 

97.5 

63.5 

94.7 

94.9 

95.2 

95.5 

95.7 

95.9 

96.2 

96.4 

96.6 

96.9 

63.0 

94.2 

94.4 

94.7 

94.9 

95.1 

95.4 

95.6 

95.9 

96.1 

96.3 

62.5 

93.6 

93.8 

94.1 

94.3 

94.6 

94.8 

95.1 

95.3 

95.5 

95.7 

62.0 

93.0 

93.2 

93.5 

93.7 

94.0 

94.2 

94.5 

94.7 

94.9 

95.1 

61.5 

92.4 

92.7 

92.9 

93.2 

93.4 

93.6 

93.9 

94.1 

94.4 

94.6 

61.0 

91.8 

92.1 

92.3 

92.6 

92.8 

93.0 

93.3 

93.5 

93.7 

93.9    1 

60.5 

91.3 

91.5 

91.7 

92.0 

92.2 

92.4 

92.7 

92.9 

93.1 

93.3    ■' 

60.0 

90.8 

91.0 

91.2 

91.5 

91.7 

91.9 

92.1 

92.4 

92.6 

92.8 

59.5 

90.2 

90.4 

90.6 

90.9 

91.1 

91.3 

91.5 

91.8 

92  0 

92.2 

59.0 

89.6 

89.8 

90.0 

90.3 

90.5 

90.7 

90.9 

91.2 

91.4 

91.6 

58.5 

89.0 

89.2 

89.4 

89.7 

89.9 

90.1 

90.3 

90.6 

90.8 

91.0 

58.0 

88.4 

88.6 

88.8 

89.1 

89.3 

89.5 

89.7 

90.0 

90.2 

90.4 

57.5 

87.8 

88.0 

88.2 

88.4 

88.7 

88.9 

89.1 

89.4 

89.6 

89.8 

57.0 

87.2 

87.4 

87.6 

87.8 

88.0 

88.3 

88.5 

88.7 

88.9 

89.1 

56.5 

86.6 

80.8 

87.0 

87.2 

87.4 

87.0 

87.8 

88.0 

88.2 

88.4 

STATION   PUBLICATIONS  AVAILABLE   FOR  FREE   DISTRIBUTION 


No. 

230. 
242. 
250. 
251. 


252. 
25i. 

255. 
257. 
261. 

262. 

263. 
264. 
266. 

267. 
268. 
270. 


271. 
272. 
273. 

274. 

275. 

276. 

277. 

No. 
114. 
115. 
117. 

124. 
126. 
127. 
128. 
129. 
131. 
133. 
135. 
136. 
137. 
138. 
139. 

140. 

142. 

143. 

144. 
147. 
148. 
151. 
152. 

153. 

154. 

155. 
156. 
157. 
158. 
160. 
162. 

164. 
165. 

166. 


Enological   Investigations. 

Humus   in  California   Soils. 

The  Loquat. 

Utilization  of  the  Nitrogen  and  Organic 
Matter  in  Septic  and  Imhoflf  Tank 
Sludges. 

Deterioration  of  Lumber. 

Irrigation  and  Soil  Conditions  in  the 
Sieira  Nevada  Foothills,  California. 

The  Citricola  Scale. 

New  Dosage  Tables. 

Melaxuma  of  the  Walnut,  "Juglans 
regia." 

Citrus  Diseases  of  Florida  and  Cuba 
Compared  vy^ith  Those  of  California. 

Size  Grades  for  Ripe  Olives. 

The  Calibration  of  the  Leakage  Meter. 

A  Spotting  of  Citrus  Fruits  Due  to  the 
Action  of  Oil  Liberated  from  the  Rind. 

Experiments  with  Stocks  for  Citrus. 

Growing  and  Grafting  Olive  Seedlings. 

A  Comparison  of  Annual  Cropping,  Bi- 
ennial Cropping,  and  Green  Manures 
on  the  Yield  of  Wheat. 

Feeding  Dairy  Calves  in  California. 

Commercial  Fertilizers. 

Preliminary  Report  on  Kearney  Vincr 
yard  Experimental  Drain. 

The  Common  Honey  Bee  as  an  Agent 
in  Prune  Pollination. 

The  Cultivation  of  Belladonna  in  Cali- 
fornia. 

The  Pomegranate. 

Sudan  Grass. 


BULLETINS 

No. 

278. 
279. 
280. 


281. 

282. 

283. 
284. 
285. 
286. 
288. 

290. 

292. 


293. 
296. 
297. 
298. 
299. 

300. 
801. 

302. 

303. 
304. 

305. 


CIRCULARS 

No. 

167. 

168. 


Increasing  the  Duty  of  Water. 

Grafting  Vinifera  Vineyards. 

The    Selection    and    Cost    of    a    Small 

Pumping   Plant.  169. 

Alfalfa  Silage  for  Fattening  Steers.  170. 
Spraying  for  the  Grape  Leaf  Hopper 

House  Fumigation.  172. 

Insecticide  Formulas.  173 
The  Control  of  Citrus  Insects. 

Spraying  for  Control  of  Walnut  Aphis.  174. 

County  Farm  Adviser.  175. 
Official  Tests  of  Dairy  Cows. 

Melilotus  Indica.  176. 
Wood  Decay  in  Orchard  Trees. 

The  Silo  in  California  Agriculture.  177. 

The   Generation   of   Hydrocyanic   Acid  179. 

Gas  in  Fumigation  by  Portable  Ma- 
chines. 181. 
Thf  Practical  Application  of  Improved 

Methods  of  Fermentation  in  Califor-  182. 

nia  Wineries  during  1913  and  1914. 

Practical  and  Inexpensive  Poultry  Ap-  183. 

pliances.  184. 

Control    of    Grasshoppers    in    Imperial  186. 

Valley.  187. 

Oidium  or  Powdery  Mildew  of  the  Vine.  188. 

Tomato  Growing  in  California.  189. 

"Lungworms."  190. 

Feeding  and  Management  of  Hogs.  191 

Some  Observations  on  the  Bulk  Hand-  193. 

ling   of    Grain    in    California.  195. 
Announcement  of  the  California   State 

Dairy  Cow  Competition,   1916-18.  197. 
Irrigation    Practice   in    Growing   Small 

Fruits  in  California.  198. 

Bovine  Tuberculosis.  200. 
How    to    operate    an    Incubator. 

Control  of  the  Penr  Scab.  201. 

Home  and  Farm  Canning.  202. 
Ijpttuce   Growing  in   California. 

White    Diarrhoea    and    Coccidiosis    of  203. 

Chicks.  204, 
Small   Fruit   Culture   in   California. 

Fundamentals   of   Sugar   Beet   Culture  205. 

under  California  Conditions.  206. 

The   County   Farm    Bureau.  207. 


Grain  Sorghums. 

Irrigation  of  Rice  in  California. 

Irrigation  of  Alfalfa  in  the  Sacramento 
Valley. 

Control  of  the  Pocket  Gopher  in  Cali- 
fornia. 

Trials  with  California  Silage  Crops  for 
Dairy  Cows. 

The  Olive  Insects  of  California. 

Irrigation  of  Alfalfa  in  Imperial  Valley. 

The  Milch  Goat  in  California. 

Commercial  Fertilizers. 

Potash  from  Tule  and  the  Fertilizer 
Value  of  Certain  Marsh  Plants. 

The  June  Drop  of  Washington  Navel 
Oranges. 

Green  Manure  Crops  in  Southern  Cali- 
fornia. 

Sweet  Sorghums  for  Forage. 

Topping  and  Pinching  Vines. 

The  Almond  in  California. 

Seedless  Raisin  Grapes. 

The  Use  of  Lumber  on  California 
Farms. 

Commercial  Fertilizers. 

California  State  Dairy  Cow  Competi- 
tion,   1916-18. 

Control  of  Ground  Squirrels  by  the 
Fumigation  Method. 

Grape  Syrup. 

A  Study  of  the  Effects  of  Freezes  on 
Citrus  in  California. 

The  Influence  of  Barley  on  the  Milk 
Secretions  of  Cows. 


Feeding    Stuffs    of    Minor    Importance. 
Spraying   for  the  Control  of  Wild  Morn- 

ing-Glory  within  the  Fog  Belt. 
The    1918   Grain   Crop. 
Fertilizing    California     Soils    for    the 

1918   Crop. 
Wheat  Culture. 
The    Construction    of   the   Wood-Hoop 

Silo. 
Farm  Drainage  Methods. 
Progress  Report  on  the  Marketing  and 

Distribution    of    Milk. 
Hog     Cholera      Prevention      and     the 

Serum   Treatment. 
Grain   Sorghums. 
Factors    of    Importance    in    Producing 

Milk  of   Low  Bacterial   Count. 
Control     of     the     California     Ground 

Squirrel. 
Extending  the  Area  of  Irrigated  Wheat 

in    California    for    1918. 
Infectious  Abortion  in  Cows. 
A  Flock  of   Sheep  on  the  Farm. 
Poultry  on  the  Farm. 
Utilizing  the   Sorghums. 
Lambing  Sheds. 
Winter   Forage   Crops. 
Agriculture  Clubs  in  California. 
Pruning  the  Seedless  Grapes. 
A    Study   of    Farm  Labor  in  California. 
Revised  Compatibility  Chart  of  Insecti- 
cides and  Fungicides. 
Suggestions    for    Increasing   Egg    Pro- 
duction  in  a  Time  of  High-Feed  Prices. 
Syrup  from   Sweet  Sorghum. 
Growing   the   Fall   or    Second   Crop  of 

Potatoes  in  California. 
Helpful    Hints    to   Hog   Raisers. 
County    Organization    for    Rural    Fire 

Control. 
Peat  as   a   Manure   Substitute. 
Handbook  of  Plant  Diseases  and  Pest 

Control. 
Blackleg. 
Jack  Cheese. 
Neufchatel  Cheese. 


